linux-kernel - Re: [RFC]mm/zsmalloc,: trigger BUG_ON in function zs_map

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Date:   Wed, 29 Mar 2017 15:42:06 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Minchan Kim <minchan@...nel.org>,
        Yisheng Xie <xieyisheng1@...wei.com>
Cc:     ngupta@...are.org, sergey.senozhatsky.work@...il.com,
        linux-mm@...ck.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Xishi Qiu <qiuxishi@...wei.com>,
        Hanjun Guo <guohanjun@...wei.com>
Subject: Re: [RFC]mm/zsmalloc,: trigger BUG_ON in function zs_map_object.

On (03/29/17 09:20), 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.
> 
> There isn't any problem with default ZS_MAX_ZSPAGE_ORDER. Right?
> So, it happens only if you changed it to 3?

I agree with Minchan. too much things could have gone wrong during the backport.

> 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?

agree again.



Yisheng, do you have this commit applied?

commit c102f07ca0b04f2cb49cfc161c83f6239d17f491
Author: Junil Lee <junil0814.lee@....com>
Date:   Wed Jan 20 14:58:18 2016 -0800

    zsmalloc: fix migrate_zspage-zs_free race condition


	-ss