From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753471Ab2HCNcn (ORCPT ); Fri, 3 Aug 2012 09:32:43 -0400 Received: from cantor2.suse.de ([195.135.220.15]:40284 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751689Ab2HCNci (ORCPT ); Fri, 3 Aug 2012 09:32:38 -0400 Date: Fri, 3 Aug 2012 15:32:35 +0200 From: Michal Hocko To: Hillf Danton Cc: Mel Gorman , Andrew Morton , Linux-MM , LKML Subject: Re: [patch] hugetlb: correct page offset index for sharing pmd Message-ID: <20120803133235.GA8434@dhcp22.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 03-08-12 20:56:45, Hillf Danton wrote: > The computation of page offset index is open coded, and incorrect, to > be used in scanning prio tree, as huge page offset is required, and is > fixed with the well defined routine. I guess that nobody reported this because if someone really wants to share he will use aligned address for mmap/shmat and so the index is 0. Anyway it is worth fixing. Thanks for pointing out! > > Signed-off-by: Hillf Danton > --- > > --- a/arch/x86/mm/hugetlbpage.c Fri Aug 3 20:34:58 2012 > +++ b/arch/x86/mm/hugetlbpage.c Fri Aug 3 20:40:16 2012 > @@ -72,12 +72,15 @@ static void huge_pmd_share(struct mm_str > if (!vma_shareable(vma, addr)) > return; > > + idx = linear_page_index(vma, addr); > + You can use linear_hugepage_index directly and remove the idx initialization as well. > mutex_lock(&mapping->i_mmap_mutex); > vma_prio_tree_foreach(svma, &iter, &mapping->i_mmap, idx, idx) { > if (svma == vma) > continue; > > - saddr = page_table_shareable(svma, vma, addr, idx); > + saddr = page_table_shareable(svma, vma, addr, > + idx * (PMD_SIZE/PAGE_SIZE)); Why not just fixing page_table_shareable as well rather than playing tricks like this? > if (saddr) { > spte = huge_pte_offset(svma->vm_mm, saddr); > if (spte) { > -- -- Michal Hocko SUSE Labs