Re: [RFC]mm/zsmalloc,: trigger BUG_ON in function zs_map_object.

[Minchan Kim]

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?

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?

> 
> 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?
> (Actuallyï 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?

> 
> Any comment is more than welcome!
> 
> Thanks
> Yisheng Xie
> 
> 
> 
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