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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 EB6F3C433E1 for ; Tue, 7 Jul 2020 11:43:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C7FC2206DF for ; Tue, 7 Jul 2020 11:43:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728014AbgGGLnR (ORCPT ); Tue, 7 Jul 2020 07:43:17 -0400 Received: from mx2.suse.de ([195.135.220.15]:46920 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727044AbgGGLnQ (ORCPT ); Tue, 7 Jul 2020 07:43:16 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 53655AE35; Tue, 7 Jul 2020 11:43:15 +0000 (UTC) Subject: Re: [PATCH v2 2/3] xen/privcmd: Mark pages as dirty To: Souptick Joarder Cc: Boris Ostrovsky , sstabellini@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, John Hubbard , Paul Durrant References: <1594059372-15563-1-git-send-email-jrdr.linux@gmail.com> <1594059372-15563-3-git-send-email-jrdr.linux@gmail.com> <8fdd8c77-27dd-2847-7929-b5d3098b1b45@suse.com> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <4abc0dd2-655c-16fa-dfc3-95904196c81f@suse.com> Date: Tue, 7 Jul 2020 13:43:12 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07.07.20 13:30, Souptick Joarder wrote: > On Tue, Jul 7, 2020 at 3:08 PM Jürgen Groß wrote: >> >> On 06.07.20 20:16, Souptick Joarder wrote: >>> pages need to be marked as dirty before unpinned it in >>> unlock_pages() which was oversight. This is fixed now. >>> >>> Signed-off-by: Souptick Joarder >>> Suggested-by: John Hubbard >>> Cc: John Hubbard >>> Cc: Boris Ostrovsky >>> Cc: Paul Durrant >>> --- >>> drivers/xen/privcmd.c | 5 ++++- >>> 1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c >>> index 33677ea..f6c1543 100644 >>> --- a/drivers/xen/privcmd.c >>> +++ b/drivers/xen/privcmd.c >>> @@ -612,8 +612,11 @@ static void unlock_pages(struct page *pages[], unsigned int nr_pages) >>> { >>> unsigned int i; >>> >>> - for (i = 0; i < nr_pages; i++) >>> + for (i = 0; i < nr_pages; i++) { >>> + if (!PageDirty(pages[i])) >>> + set_page_dirty_lock(pages[i]); >> >> With put_page() directly following I think you should be able to use >> set_page_dirty() instead, as there is obviously a reference to the page >> existing. > > Patch [3/3] will convert above codes to use unpin_user_pages_dirty_lock() > which internally do the same check. So I thought to keep linux-stable and > linux-next code in sync. John had a similar concern [1] and later agreed to keep > this check. > > Shall I keep this check ? No ? > > [1] https://lore.kernel.org/xen-devel/a750e5e5-fd5d-663b-c5fd-261d7c939ba7@nvidia.com/ I wasn't referring to checking PageDirty(), but to the use of set_page_dirty_lock(). Looking at the comment just before the implementation of set_page_dirty_lock() suggests that it is fine to use set_page_dirty() instead (so not calling lock_page()). Only the transition from get_user_pages_fast() to pin_user_pages_fast() requires to use the locked version IMO. Juergen