From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753156Ab2H0Kj0 (ORCPT ); Mon, 27 Aug 2012 06:39:26 -0400 Received: from e06smtp17.uk.ibm.com ([195.75.94.113]:56308 "EHLO e06smtp17.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752153Ab2H0KjZ (ORCPT ); Mon, 27 Aug 2012 06:39:25 -0400 Date: Mon, 27 Aug 2012 12:39:17 +0200 From: Gerald Schaefer To: Hillf Danton Cc: akpm@linux-foundation.org, aarcange@redhat.com, linux-mm@kvack.org, ak@linux.intel.com, hughd@google.com, linux-kernel@vger.kernel.org, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com Subject: Re: [RFC patch 3/7] thp: make MADV_HUGEPAGE check for mm->def_flags Message-ID: <20120827123917.3313dfda@thinkpad> In-Reply-To: References: <20120823171733.595087166@de.ibm.com> <20120823171854.580076595@de.ibm.com> Reply-To: gerald.schaefer@de.ibm.com X-Mailer: Claws Mail 3.7.9 (GTK+ 2.24.6; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit x-cbid: 12082710-0542-0000-0000-000002D7C8C4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 25 Aug 2012 20:47:37 +0800 Hillf Danton wrote: > On Fri, Aug 24, 2012 at 1:17 AM, Gerald Schaefer > wrote: > > This adds a check to hugepage_madvise(), to refuse MADV_HUGEPAGE > > if VM_NOHUGEPAGE is set in mm->def_flags. On System z, the VM_NOHUGEPAGE > > flag will be set in mm->def_flags for kvm processes, to prevent any > > future thp mappings. In order to also prevent MADV_HUGEPAGE on such an > > mm, hugepage_madvise() should check mm->def_flags. > > > > Signed-off-by: Gerald Schaefer > > --- > > mm/huge_memory.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -1464,6 +1464,8 @@ out: > > int hugepage_madvise(struct vm_area_struct *vma, > > unsigned long *vm_flags, int advice) > > { > > + struct mm_struct *mm = vma->vm_mm; > > + > > switch (advice) { > > case MADV_HUGEPAGE: > > /* > > @@ -1471,6 +1473,8 @@ int hugepage_madvise(struct vm_area_stru > > */ > > if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) > > return -EINVAL; > > + if (mm->def_flags & VM_NOHUGEPAGE) > > + return -EINVAL; > > Looks ifdefinery needed for s390 to wrap the added check, and > a brief comment? Hmm, architecture #ifdefs in common code are ugly. I'd rather keep the check even if it is redundant right now for other architectures than s390. It is not a performance critical path, and there may be other users of that in the future.