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 S1754211AbdC2HxD (ORCPT <rfc822;w@1wt.eu>);
        Wed, 29 Mar 2017 03:53:03 -0400
Received: from szxga02-in.huawei.com ([45.249.212.188]:4844 "EHLO
        dggrg02-dlp.huawei.com" rhost-flags-OK-FAIL-OK-FAIL)
        by vger.kernel.org with ESMTP id S1753716AbdC2HxB (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 29 Mar 2017 03:53:01 -0400
From: Yisheng Xie <xieyisheng1@huawei.com>
Subject: Re: [RFC]mm/zsmalloc,: trigger BUG_ON in function zs_map_object.
To: Minchan Kim <minchan@kernel.org>
References: <e8aa282e-ad53-bfb8-2b01-33d2779f247a@huawei.com>
 <20170329002029.GA18979@bbox>
CC: <ngupta@vflare.org>, <sergey.senozhatsky.work@gmail.com>,
        <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Xishi Qiu <qiuxishi@huawei.com>, Hanjun Guo <guohanjun@huawei.com>
Message-ID: <4026833d-d639-eb62-c3a8-5c3403ab105f@huawei.com>
Date: Wed, 29 Mar 2017 15:51:23 +0800
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101
 Thunderbird/45.1.0
MIME-Version: 1.0
In-Reply-To: <20170329002029.GA18979@bbox>
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 8bit
X-Originating-IP: [10.177.29.40]
X-CFilter-Loop: Reflected
X-Mirapoint-Virus-RAPID-Raw: score=unknown(0),
        refid=str=0001.0A0B0206.58DB67D0.0197,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: b8c4ccf6664ea8bf7c03e0529a362986
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi Minchan,

Thanks for your comment!
On 2017/3/29 8:20, Minchan Kim wrote:
> Hello,
> 
> On Tue, Mar 28, 2017 at 03:20:22PM +0800, Yisheng Xie wrote:
>> Hi, all,
>>
>> We had backport the no-lru migration to linux-4.1, meanwhile change the
>> ZS_MAX_ZSPAGE_ORDER to 3. Then we met a BUG_ON(!page[1]).
> 
> Hmm, I don't know how you backported.
Yes, maybe caused by our unsuitable backport.

> 
> There isn't any problem with default ZS_MAX_ZSPAGE_ORDER. Right?
> So, it happens only if you changed it to 3?
I will check whether it will default ZS_MAX_ZSPAGE_ORDER.

> 
> Could you tell me what is your base kernel? and what zram/zsmalloc
> version(ie, from what kernel version) you backported to your
> base kernel?
> 
We backport from kernel v4.8-rc8 to kernel v4.1.

>>
>> It rarely happen, and presently, what I get is:
>> [6823.316528s]obj=a160701f, obj_idx=15, class{size:2176,objs_per_zspage:15,pages_per_zspage:8}
>> [...]
>> [6823.316619s]BUG: failure at /home/ethan/kernel/linux-4.1/mm/zsmalloc.c:1458/zs_map_object()! ----> BUG_ON(!page[1])
>>
>> It seems that we have allocated an object from a ZS_FULL group?
>> (Actually， I do not get the inuse number of this zspage, which I am trying to.)
>> And presently, I can not find why it happened. Any idea about it?
> 
> Although it happens rarely, always above same symptom once it happens?
Yes , though the class size is not the same, which means not from the same class.
however, the (obj_idx == objs_per_zspage) is always true.

Thanks
Yisheng Xie.