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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 19E95C2D0DB for ; Thu, 23 Jan 2020 13:11:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D9D1B24655 for ; Thu, 23 Jan 2020 13:11:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D9D1B24655 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6D4246B0006; Thu, 23 Jan 2020 08:11:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 685026B0007; Thu, 23 Jan 2020 08:11:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 59B796B0008; Thu, 23 Jan 2020 08:11:17 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0215.hostedemail.com [216.40.44.215]) by kanga.kvack.org (Postfix) with ESMTP id 436636B0006 for ; Thu, 23 Jan 2020 08:11:17 -0500 (EST) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id F1A8B824556B for ; Thu, 23 Jan 2020 13:11:16 +0000 (UTC) X-FDA: 76408934952.11.roof16_b113914add37 X-HE-Tag: roof16_b113914add37 X-Filterd-Recvd-Size: 2645 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by imf09.hostedemail.com (Postfix) with ESMTP for ; Thu, 23 Jan 2020 13:11:15 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Jan 2020 05:11:14 -0800 X-IronPort-AV: E=Sophos;i="5.70,354,1574150400"; d="scan'208";a="220660992" Received: from jnikula-mobl3.fi.intel.com (HELO localhost) ([10.237.66.161]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Jan 2020 05:11:08 -0800 From: Jani Nikula To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Linus Torvalds , Alexander Viro , Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, dri-devel@lists.freedesktop.org, x86@kernel.org Subject: Re: [PATCH v3 2/7] uaccess: Tell user_access_begin() if it's for a write or not In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: Date: Thu, 23 Jan 2020 15:11:05 +0200 Message-ID: <8736c6e2s6.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 23 Jan 2020, Christophe Leroy wrote: > On 32 bits powerPC (book3s/32), only write accesses to user are > protected and there is no point spending time on unlocking for reads. > > On 64 bits powerpc (book3s/64 at least), access can be granted > read only, write only or read/write. > > Add an argument to user_access_begin() to tell when it's for write and > return an opaque key that will be used by user_access_end() to know > what was done by user_access_begin(). IMHO an opaque key is a prime example of a case where the use of an opaque typedef is warranted. Nobody needs to know or care it's specifically an unsigned long. BR, Jani. -- Jani Nikula, Intel Open Source Graphics Center