Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758008Ab3CTGNz (ORCPT ); Wed, 20 Mar 2013 02:13:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:21597 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757958Ab3CTGNx (ORCPT ); Wed, 20 Mar 2013 02:13:53 -0400 Date: Wed, 20 Mar 2013 02:12:54 -0400 From: Naoya Horiguchi To: Michal Hocko Cc: linux-mm@kvack.org, Andrew Morton , Mel Gorman , Hugh Dickins , KOSAKI Motohiro , Andi Kleen , linux-kernel@vger.kernel.org Message-ID: <1363759974-38t0k25g-mutt-n-horiguchi@ah.jp.nec.com> In-Reply-To: <20130319071113.GD5112@dhcp22.suse.cz> References: <1361475708-25991-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1361475708-25991-6-git-send-email-n-horiguchi@ah.jp.nec.com> <20130318154057.GS10192@dhcp22.suse.cz> <1363651636-3lsf20se-mutt-n-horiguchi@ah.jp.nec.com> <20130319071113.GD5112@dhcp22.suse.cz> Subject: Re: [PATCH 5/9] migrate: enable migrate_pages() to migrate hugepage Mime-Version: 1.0 Content-Type: text/plain; charset=iso-2022-jp Content-Transfer-Encoding: 7bit Content-Disposition: inline X-Mutt-Fcc: ~/Maildir/sent/ 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 Content-Length: 1894 Lines: 42 On Tue, Mar 19, 2013 at 08:11:13AM +0100, Michal Hocko wrote: > On Mon 18-03-13 20:07:16, Naoya Horiguchi wrote: > > On Mon, Mar 18, 2013 at 04:40:57PM +0100, Michal Hocko wrote: > > > On Thu 21-02-13 14:41:44, Naoya Horiguchi wrote: ... > > > > @@ -536,6 +557,11 @@ static inline int check_pmd_range(struct vm_area_struct *vma, pud_t *pud, > > > > pmd = pmd_offset(pud, addr); > > > > do { > > > > next = pmd_addr_end(addr, end); > > > > + if (pmd_huge(*pmd) && is_vm_hugetlb_page(vma)) { > > > > > > Why an explicit check for is_vm_hugetlb_page here? Isn't pmd_huge() > > > sufficient? > > > > I think we need both check here because if we use only pmd_huge(), > > pmd for thp goes into this branch wrongly. > > Bahh. You are right. I thought that pmd_huge is hugetlb thingy but it > obviously checks only _PAGE_PSE same as pmd_large() which is really > unfortunate and confusing. Can we make it hugetlb specific? I agree that we had better fix this confusion. What pmd_huge() (or pmd_large() in some architectures) does is just checking whether a given pmd is pointing to huge/large page or not. It does not say which type of hugepage it is. So it shouldn't be used to decide whether the hugepage are hugetlbfs or not. I think it would be better to introduce pmd_hugetlb() which has pmd and vma as arguments and returns true only for hugetlbfs pmd. Checking pmd_hugetlb() should come before checking pmd_trans_huge() because pmd_trans_huge() implicitly assumes that the vma which covers the virtual address of a given pmd is not hugetlbfs vma. I'm interested in this cleanup, so will work on it after this patchset. Thanks, Naoya -- 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/