From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f44.google.com (mail-pa0-f44.google.com [209.85.220.44]) by kanga.kvack.org (Postfix) with ESMTP id 40D766B0036 for ; Wed, 14 May 2014 23:34:34 -0400 (EDT) Received: by mail-pa0-f44.google.com with SMTP id ld10so478581pab.17 for ; Wed, 14 May 2014 20:34:33 -0700 (PDT) Received: from mail-pa0-x22a.google.com (mail-pa0-x22a.google.com [2607:f8b0:400e:c03::22a]) by mx.google.com with ESMTPS id ef1si1967861pbc.128.2014.05.14.20.34.33 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 14 May 2014 20:34:33 -0700 (PDT) Received: by mail-pa0-f42.google.com with SMTP id rd3so480532pab.15 for ; Wed, 14 May 2014 20:34:33 -0700 (PDT) Message-ID: <1400124866.26173.19.camel@cyc> Subject: Re: [PATCH] mm/memory-failure.c: fix memory leak by race between poison and unpoison From: cyc Date: Thu, 15 May 2014 11:34:26 +0800 In-Reply-To: <1400080891-5145-1-git-send-email-n-horiguchi@ah.jp.nec.com> References: <1400080891-5145-1-git-send-email-n-horiguchi@ah.jp.nec.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: Andrew Morton , Andi Kleen , Wu Fengguang , linux-kernel@vger.kernel.org, linux-mm@kvack.org a?? 2014-05-14a,?c?? 11:21 -0400i 1/4 ?Naoya Horiguchia??e??i 1/4 ? > When a memory error happens on an in-use page or (free and in-use) hugepage, > the victim page is isolated with its refcount set to one. When you try to > unpoison it later, unpoison_memory() calls put_page() for it twice in order to > bring the page back to free page pool (buddy or free hugepage list.) > However, if another memory error occurs on the page which we are unpoisoning, > memory_failure() returns without releasing the refcount which was incremented > in the same call at first, which results in memory leak and unconsistent > num_poisoned_pages statistics. This patch fixes it. We assume that a new memory error occurs on the hugepage which we are unpoisoning. A unpoisoned B poisoned C hugepage: |---------------+++++++++++++++++| There are two cases, so shown. 1. the victim page belongs to A-B, the memory_failure will be blocked by lock_page() until unlock_page() invoked by unpoison_memory(). 2. the victim page belongs to B-C, the memory_failure() will return very soon at the beginning of this function. So the new memory error will have no effect what you say so. thx! cyc > > Signed-off-by: Naoya Horiguchi > Cc: [2.6.32+] > --- > mm/memory-failure.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git next-20140512.orig/mm/memory-failure.c next-20140512/mm/memory-failure.c > index 9872af1b1e9d..93a08bd78c78 100644 > --- next-20140512.orig/mm/memory-failure.c > +++ next-20140512/mm/memory-failure.c > @@ -1153,6 +1153,8 @@ int memory_failure(unsigned long pfn, int trapno, int flags) > */ > if (!PageHWPoison(p)) { > printk(KERN_ERR "MCE %#lx: just unpoisoned\n", pfn); > + atomic_long_sub(nr_pages, &num_poisoned_pages); > + put_page(hpage); > res = 0; > goto out; > } -- 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