Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753842Ab3HVQng (ORCPT ); Thu, 22 Aug 2013 12:43:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:9246 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753051Ab3HVQnf (ORCPT ); Thu, 22 Aug 2013 12:43:35 -0400 Date: Thu, 22 Aug 2013 12:43:08 -0400 From: Naoya Horiguchi To: Wanpeng Li Cc: Andrew Morton , Andi Kleen , Fengguang Wu , Tony Luck , gong.chen@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Message-ID: <1377189788-xv5ewgmb-mutt-n-horiguchi@ah.jp.nec.com> In-Reply-To: <1377164907-24801-3-git-send-email-liwanp@linux.vnet.ibm.com> References: <1377164907-24801-1-git-send-email-liwanp@linux.vnet.ibm.com> <1377164907-24801-3-git-send-email-liwanp@linux.vnet.ibm.com> Subject: Re: [PATCH 3/6] mm/hwpoison: fix num_poisoned_pages error statistics for thp Mime-Version: 1.0 Content-Type: text/plain; charset=iso-2022-jp Content-Transfer-Encoding: 7bit Content-Disposition: inline X-Mutt-References: <1377164907-24801-3-git-send-email-liwanp@linux.vnet.ibm.com> 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: 1964 Lines: 47 On Thu, Aug 22, 2013 at 05:48:24PM +0800, Wanpeng Li wrote: > There is a race between hwpoison page and unpoison page, memory_failure > set the page hwpoison and increase num_poisoned_pages without hold page > lock, and one page count will be accounted against thp for num_poisoned_pages. > However, unpoison can occur before memory_failure hold page lock and > split transparent hugepage, unpoison will decrease num_poisoned_pages > by 1 << compound_order since memory_failure has not yet split transparent > hugepage with page lock held. That means we account one page for hwpoison > and 1 << compound_order for unpoison. This patch fix it by decrease one > account for num_poisoned_pages against no hugetlbfs pages case. > > Signed-off-by: Wanpeng Li I think that a thp never becomes hwpoisoned without splitting, so "trying to unpoison thp" never happens (I think that this implicit fact should be commented somewhere or asserted with VM_BUG_ON().) And nr_pages in unpoison_memory() can be greater than 1 for hugetlbfs page. So does this patch break counting when unpoisoning free hugetlbfs pages? Thanks, Naoya Horiguchi > --- > mm/memory-failure.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index 5092e06..6bfd51e 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -1350,7 +1350,7 @@ int unpoison_memory(unsigned long pfn) > return 0; > } > if (TestClearPageHWPoison(p)) > - atomic_long_sub(nr_pages, &num_poisoned_pages); > + atomic_long_dec(&num_poisoned_pages); > pr_info("MCE: Software-unpoisoned free page %#lx\n", pfn); > return 0; > } > -- > 1.8.1.2 > -- 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/