linux-kernel - Re: [RFC] propagate gfp_t to page table alloc functions

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Date:	Tue, 24 Apr 2012 14:35:10 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	kosaki.motohiro@...fujitsu.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [RFC] propagate gfp_t to page table alloc functions

On 04/24/2012 02:16 PM, KAMEZAWA Hiroyuki wrote:

> (2012/04/23 17:55), Minchan Kim wrote:
> 
>> As I test some code, I found a problem about deadlock by lockdep.
>> The reason I saw the message is __vmalloc calls map_vm_area which calls
>> pud/pmd_alloc without gfp_t. so although we call __vmalloc with
>> GFP_ATOMIC or GFP_NOIO, it ends up allocating pages with GFP_KERNEL.
>> The should be a BUG. This patch fixes it by passing gfp_to to low page
>> table allocate functions.
>>
>> Signed-off-by: Minchan Kim <minchan@...nel.org>
> 
> 
> Hmm ? vmalloc should support GFP_ATOMIC ?


I'm not sure but alloc_large_system_hash already has used.
And it's not specific on GFP_ATOMIC.
We have to care of GFP_NOFS and GFP_NOIO to prevent deadlock on reclaim
context.
There are some places to use GFP_NOFS and we don't emit any warning
message in case of that.

> 
> And, do we need to change all pud_,pgd_,pmd_,pte_alloc() for users pgtables ?


Maybe.


-- 
Kind regards,
Minchan Kim
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