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 S1755609AbcJZJPv (ORCPT <rfc822;w@1wt.eu>);
        Wed, 26 Oct 2016 05:15:51 -0400
Received: from mail-wm0-f45.google.com ([74.125.82.45]:34866 "EHLO
        mail-wm0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751802AbcJZJPt (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 26 Oct 2016 05:15:49 -0400
Date: Wed, 26 Oct 2016 11:15:43 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: linux-mm@kvack.org, Linus Torvalds <torvalds@linux-foundation.org>,
        Jan Kara <jack@suse.cz>, Hugh Dickins <hughd@google.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Rik van Riel <riel@redhat.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls
Message-ID: <20161026091542.GD18382@dhcp22.suse.cz>
References: <20161025233609.5601-1-lstoakes@gmail.com>
 <20161025234631.GA5946@lucifer>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20161025234631.GA5946@lucifer>
User-Agent: Mutt/1.6.0 (2016-04-01)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed 26-10-16 00:46:31, Lorenzo Stoakes wrote:
> The holdout for unexporting __get_user_pages_unlocked() is its invocation in
> mm/process_vm_access.c: process_vm_rw_single_vec(), as this definitely _does_
> seem to invoke VM_FAULT_RETRY behaviour which get_user_pages_remote() will not
> trigger if we were to replace it with the latter.

I am not sure I understand. Prior to 1e9877902dc7e this used
get_user_pages_unlocked. What prevents us from reintroducing it with
FOLL_REMOVE which was meant to be added by the above commit?

Or am I missing your point?
-- 
Michal Hocko
SUSE Labs