linux-kernel - Re: [PATCH] mm: move page_ext_init after all struct pages are initialized

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Date:	Thu, 19 May 2016 16:26:09 -0700
From:	"Shi, Yang" <yang.shi@...aro.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	iamjoonsoo.kim@....com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH] mm: move page_ext_init after all struct pages are
 initialized

On 5/19/2016 4:21 PM, Andrew Morton wrote:
> On Thu, 19 May 2016 15:35:15 -0700 "Shi, Yang" <yang.shi@...aro.org> wrote:
>
>> On 5/19/2016 3:30 PM, Andrew Morton wrote:
>>> On Thu, 19 May 2016 14:29:05 -0700 Yang Shi <yang.shi@...aro.org> wrote:
>>>
>>>> When DEFERRED_STRUCT_PAGE_INIT is enabled, just a subset of memmap at boot
>>>> are initialized, then the rest are initialized in parallel by starting one-off
>>>> "pgdatinitX" kernel thread for each node X.
>>>>
>>>> If page_ext_init is called before it, some pages will not have valid extension,
>>>> so move page_ext_init() after it.
>>>>
>>>
>>> <stdreply>When fixing a bug, please fully describe the end-user impact
>>> of that bug</>
>>
>> The kernel ran into the below oops which is same with the oops reported
>> in
>> http://ozlabs.org/~akpm/mmots/broken-out/mm-page_is_guard-return-false-when-page_ext-arrays-are-not-allocated-yet.patch.
>
> So this patch makes
> mm-page_is_guard-return-false-when-page_ext-arrays-are-not-allocated-yet.patch
> obsolete?

Actually, no. Checking the return value for lookup_page_ext() is still 
needed. But, the commit log need to be amended since that bootup oops 
won't happen anymore with this patch applied.

Thanks,
Yang

>