linux-kernel - Re: [v2 PATCH] mm: move page_ext_init after all struct pages are initialized

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Message-ID: <f0c27d67-3735-300b-76eb-e49d56ab7a10@linaro.org>
Date:	Fri, 20 May 2016 08:41:09 -0700
From:	"Shi, Yang" <yang.shi@...aro.org>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	akpm@...ux-foundation.org, iamjoonsoo.kim@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linaro-kernel@...ts.linaro.org
Subject: Re: [v2 PATCH] mm: move page_ext_init after all struct pages are
 initialized

On 5/20/2016 6:16 AM, Michal Hocko wrote:
> On Thu 19-05-16 15:13:26, Yang Shi wrote:
> [...]
>> diff --git a/init/main.c b/init/main.c
>> index b3c6e36..2075faf 100644
>> --- a/init/main.c
>> +++ b/init/main.c
>> @@ -606,7 +606,6 @@ asmlinkage __visible void __init start_kernel(void)
>>  		initrd_start = 0;
>>  	}
>>  #endif
>> -	page_ext_init();
>>  	debug_objects_mem_init();
>>  	kmemleak_init();
>>  	setup_per_cpu_pageset();
>> @@ -1004,6 +1003,8 @@ static noinline void __init kernel_init_freeable(void)
>>  	sched_init_smp();
>>
>>  	page_alloc_init_late();
>> +	/* Initialize page ext after all struct pages are initializaed */
>> +	page_ext_init();
>>
>>  	do_basic_setup();
>
> I might be missing something but don't we have the same problem with
> CONFIG_FLATMEM? page_ext_init_flatmem is called way earlier. Or
> CONFIG_DEFERRED_STRUCT_PAGE_INIT is never enabled for CONFIG_FLATMEM?

Yes, CONFIG_DEFERRED_STRUCT_PAGE_INIT depends on MEMORY_HOTPLUG which 
depends on SPARSEMEM. So, this config is not valid for FLATMEM at all.

Thanks,
Yang

>