linux-kernel - Re: [PATCH 09/12] thp: introduce khugepaged_prealloc_page and khugepaged_alloc

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Date:	Thu, 13 Sep 2012 17:26:06 +0800
From:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
To:	Hugh Dickins <hughd@...gle.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Michel Lespinasse <walken@...gle.com>,
	David Rientjes <rientjes@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH 09/12] thp: introduce khugepaged_prealloc_page and khugepaged_alloc_page

On 09/13/2012 02:27 PM, Hugh Dickins wrote:
> On Wed, 12 Sep 2012, Xiao Guangrong wrote:
>> On 09/12/2012 10:03 AM, Hugh Dickins wrote:
>>
>>> What brought me to look at it was hitting "BUG at mm/huge_memory.c:1842!"
>>> running tmpfs kbuild swapping load (with memcg's memory.limit_in_bytes
>>> forcing out to swap), while I happened to have CONFIG_NUMA=y.
>>>
>>> That's the VM_BUG_ON(*hpage) on entry to khugepaged_alloc_page().
>>
>>>
>>> So maybe 9/12 is just obscuring what was already a BUG, either earlier
>>> in your series or elsewhere in mmotm (I've never seen it on 3.6-rc or
>>> earlier releases, nor without CONFIG_NUMA).  I've not spent any time
>>> looking for it, maybe it's obvious - can you spot and fix it?
>>
>> Hugh,
>>
>> I think i have already found the reason,
> 
> Great, thank you.
> 
>> if i am correct, the bug was existing before my patch.
> 
> Before your patchset?  Are you sure of that?

No. :)

I have told Andrew that the fix patch need not back port in
0/3. Sorry again for my mistake.

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