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 S967830AbdIZH5N (ORCPT <rfc822;w@1wt.eu>);
        Tue, 26 Sep 2017 03:57:13 -0400
Received: from szxga04-in.huawei.com ([45.249.212.190]:7000 "EHLO
        szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S965054AbdIZH5J (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 26 Sep 2017 03:57:09 -0400
Message-ID: <59CA0847.8000508@huawei.com>
Date: Tue, 26 Sep 2017 15:56:55 +0800
From: Xishi Qiu <qiuxishi@huawei.com>
User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:12.0) Gecko/20120428 Thunderbird/12.0.1
MIME-Version: 1.0
To: Michal Hocko <mhocko@kernel.org>, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Mel Gorman <mgorman@techsingularity.net>
CC: Linux MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>,
        "zhong jiang" <zhongjiang@huawei.com>,
        yeyunfeng <yeyunfeng@huawei.com>, <wanghaitao12@huawei.com>,
        "Zhoukang (A)" <zhoukang7@huawei.com>
Subject: [RFC] a question about mlockall() and mprotect()
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 7bit
X-Originating-IP: [10.177.25.179]
X-CFilter-Loop: Reflected
X-Mirapoint-Virus-RAPID-Raw: score=unknown(0),
        refid=str=0001.0A0B0201.59CA0852.00CE,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0,
        ip=0.0.0.0,
        so=2014-11-16 11:51:01,
        dmn=2013-03-21 17:37:32
X-Mirapoint-Loop-Id: 35cfd41902834122c240ba04c19bde73
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

When we call mlockall(), we will add VM_LOCKED to the vma,
if the vma prot is ---p, then mm_populate -> get_user_pages
will not alloc memory.

I find it said "ignore errors" in mm_populate()
static inline void mm_populate(unsigned long addr, unsigned long len)
{
	/* Ignore errors */
	(void) __mm_populate(addr, len, 1);
}

And later we call mprotect() to change the prot, then it is
still not alloc memory for the mlocked vma.

My question is that, shall we alloc memory if the prot changed,
and who(kernel, glibc, user) should alloc the memory?

Thanks,
Xishi Qiu