From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f46.google.com (mail-pb0-f46.google.com [209.85.160.46]) by kanga.kvack.org (Postfix) with ESMTP id 43DEF6B017C for ; Wed, 19 Mar 2014 16:33:08 -0400 (EDT) Received: by mail-pb0-f46.google.com with SMTP id rq2so9461425pbb.33 for ; Wed, 19 Mar 2014 13:33:07 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTP id bo2si69139pbb.250.2014.03.19.13.33.07 for ; Wed, 19 Mar 2014 13:33:07 -0700 (PDT) Date: Wed, 19 Mar 2014 13:33:05 -0700 From: Andrew Morton Subject: Re: [PATCH RESEND -mm 2/2] mm/mempolicy.c: add comment in queue_pages_hugetlb() Message-Id: <20140319133305.13cb7a03f6bd3745889f65b3@linux-foundation.org> In-Reply-To: <1395196179-4075-2-git-send-email-n-horiguchi@ah.jp.nec.com> References: <1395196179-4075-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1395196179-4075-2-git-send-email-n-horiguchi@ah.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: Sasha Levin , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Tue, 18 Mar 2014 22:29:39 -0400 Naoya Horiguchi wrote: > We have a race where we try to migrate an invalid page, resulting in > hitting VM_BUG_ON_PAGE in isolate_huge_page(). > queue_pages_hugetlb() is OK to fail, so let's check !PageHeadHuge to keep > invalid hugepage from queuing. > > .. > > --- v3.14-rc7-mmotm-2014-03-18-16-37.orig/mm/mempolicy.c > +++ v3.14-rc7-mmotm-2014-03-18-16-37/mm/mempolicy.c > @@ -530,6 +530,17 @@ static int queue_pages_hugetlb(pte_t *pte, unsigned long addr, > if (!pte_present(entry)) > return 0; > page = pte_page(entry); > + > + /* > + * Trinity found that page could be a non-hugepage. This is an > + * unexpected behavior, but it's not clear how this problem happens. > + * So let's simply skip such corner case. Page migration can often > + * fail for various reasons, so it's ok to just skip the address > + * unsuitable to hugepage migration. > + */ > + if (!PageHeadHuge(page)) > + return 0; > + Whoa, we won't be doing this thanks. The day we resort to this sort of thing is the day we revert to the 2.2.26 VM. I suppose I'd be OK with putting if (WARN_ON(!PageHeadHuge(page))) return 0; in there as a temporary be-kind-to-testers thing, but we must get a full understanding of what's happening in there. Was this problem caused by or exposed by the pagetable walker patches? -- 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