From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx197.postini.com [74.125.245.197]) by kanga.kvack.org (Postfix) with SMTP id C7CAB6B00B2 for ; Wed, 8 May 2013 10:33:08 -0400 (EDT) Received: by mail-qa0-f44.google.com with SMTP id o13so2796735qaj.17 for ; Wed, 08 May 2013 07:33:07 -0700 (PDT) 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 Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: KOSAKI Motohiro Cc: "linux-mm@kvack.org" , LKML , Jerome Glisse 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org