From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx109.postini.com [74.125.245.109]) by kanga.kvack.org (Postfix) with SMTP id 6B20D6B0033 for ; Thu, 22 Aug 2013 13:00:59 -0400 (EDT) Date: Thu, 22 Aug 2013 13:00:37 -0400 From: Naoya Horiguchi Message-ID: <1377190837-ry9saqra-mutt-n-horiguchi@ah.jp.nec.com> In-Reply-To: <1377189788-xv5ewgmb-mutt-n-horiguchi@ah.jp.nec.com> References: <1377164907-24801-1-git-send-email-liwanp@linux.vnet.ibm.com> <1377164907-24801-3-git-send-email-liwanp@linux.vnet.ibm.com> <1377189788-xv5ewgmb-mutt-n-horiguchi@ah.jp.nec.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 Sender: owner-linux-mm@kvack.org List-ID: 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 On Thu, Aug 22, 2013 at 12:43:08PM -0400, Naoya Horiguchi wrote: > 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? Sorry, the latter part of this remark was incorrect. Please ignore it. - Naoya -- 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