Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756129Ab3EHOdK (ORCPT ); Wed, 8 May 2013 10:33:10 -0400 Received: from mail-qc0-f180.google.com ([209.85.216.180]:63048 "EHLO mail-qc0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754585Ab3EHOdI (ORCPT ); Wed, 8 May 2013 10:33:08 -0400 MIME-Version: 1.0 In-Reply-To: References: <1367967522-3934-1-git-send-email-j.glisse@gmail.com> Date: Wed, 8 May 2013 10:33:07 -0400 Message-ID: Subject: Re: [PATCH] mm: honor FOLL_GET flag in follow_hugetlb_page v2 From: Jerome Glisse To: KOSAKI Motohiro Cc: "linux-mm@kvack.org" , LKML , Jerome Glisse Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1605 Lines: 35 On Tue, May 7, 2013 at 10:41 PM, KOSAKI Motohiro wrote: > On Tue, May 7, 2013 at 8:51 PM, Jerome Glisse wrote: >> On Tue, May 7, 2013 at 8:47 PM, KOSAKI Motohiro >> wrote: >>> On Tue, May 7, 2013 at 6:58 PM, wrote: >>>> From: Jerome Glisse >>>> >>>> Do not increase page count if FOLL_GET is not set. None of the >>>> current user can trigger the issue because none of the current >>>> user call __get_user_pages with both the pages array ptr non >>>> NULL and the FOLL_GET flags non set in other word all caller >>>> of __get_user_pages that don't set the FOLL_GET flags also call >>>> with pages == NULL. >>> >>> Because, __get_user_pages() doesn't allow pages==NULL and FOLL_GET is on. >> >> Yes but this allow pages != NULL and FOLL_GET not set and as i said >> there is no such user of that yet and this is exactly what i was >> trying to use. > > Why? The following bug_on inhibit both case. Yes i get lost on the double negation, but still my patch is correct and i am not using gup but follow_hugetlb_page directly and i run into the issue. My patch does not change the behavior for current user, just fix assumption new user might have when not setting the FOLL_GET flags. >>> VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET)); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/