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

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Date:   Tue, 28 Mar 2017 15:20:22 +0800
From:   Yisheng Xie <xieyisheng1@...wei.com>
To:     <minchan@...nel.org>, <ngupta@...are.org>,
        <sergey.senozhatsky.work@...il.com>
CC:     <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Xishi Qiu <qiuxishi@...wei.com>,
        Hanjun Guo <guohanjun@...wei.com>
Subject: [RFC]mm/zsmalloc,: trigger BUG_ON in function zs_map_object.

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]).

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?

Any comment is more than welcome!

Thanks
Yisheng Xie