From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753213AbbDCBEG (ORCPT <rfc822;w@1wt.eu>);
	Thu, 2 Apr 2015 21:04:06 -0400
Received: from mail-ie0-f180.google.com ([209.85.223.180]:33767 "EHLO
	mail-ie0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751751AbbDCBED (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Thu, 2 Apr 2015 21:04:03 -0400
Date: Thu, 2 Apr 2015 18:04:00 -0700 (PDT)
From: David Rientjes <rientjes@google.com>
X-X-Sender: rientjes@chino.kir.corp.google.com
To: Andrey Ryabinin <a.ryabinin@samsung.com>
cc: Andrew Morton <akpm@linux-foundation.org>,
        Dave Kleikamp <shaggy@kernel.org>, Christoph Hellwig <hch@lst.de>,
        Sebastian Ott <sebott@linux.vnet.ibm.com>,
        Mikulas Patocka <mpatocka@redhat.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        jfs-discussion@lists.sourceforge.net
Subject: Re: [patch v2 4/4] mm, mempool: poison elements backed by page
 allocator
In-Reply-To: <551A861B.7020701@samsung.com>
Message-ID: <alpine.DEB.2.10.1504021803170.20229@chino.kir.corp.google.com>
References: <alpine.DEB.2.10.1503241607240.21805@chino.kir.corp.google.com> <alpine.DEB.2.10.1503241609370.21805@chino.kir.corp.google.com> <CAPAsAGwipUr7NBWjQ_xjA0CfeiZ0NuYAg13M4jYmWVe4V8Jjmg@mail.gmail.com> <alpine.DEB.2.10.1503261542060.16259@chino.kir.corp.google.com>
 <551A861B.7020701@samsung.com>
User-Agent: Alpine 2.10 (DEB 1266 2009-07-14)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, 31 Mar 2015, Andrey Ryabinin wrote:

> > We don't have a need to set PAGE_EXT_DEBUG_POISON on these pages sitting 
> > in the reserved pool, nor do we have a need to do kmap_atomic() since it's 
> > already mapped and must be mapped to be on the reserved pool, which is 
> > handled by mempool_free().
> > 
> 
> Hmm.. I just realized that this statement might be wrong.
> Why pages has to be mapped to be on reserved pool?
> mempool could be used for highmem pages and there is no need to kmap()
> until these pages will be used.
> 
> drbd (drivers/block/drbd) already uses mempool for highmem pages:
> 

Yes, you're exactly right, I didn't see this because the mempool is 
created in one file and then solely used in another file, but regardless 
we still need protection from this usecase.