linux-kernel - Re: [PATCH 1/9] migrate: add migrate_entry_wait

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Message-ID: <515D083A.4010704@gmail.com>
Date:	Thu, 04 Apr 2013 12:57:30 +0800
From:	Simon Jeons <simon.jeons@...il.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
CC:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, Hugh Dickins <hughd@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/9] migrate: add migrate_entry_wait_huge()

Ping!
On 03/21/2013 07:36 AM, Simon Jeons wrote:
> Hi Naoya,
> On 03/21/2013 05:53 AM, Naoya Horiguchi wrote:
>> On Wed, Mar 20, 2013 at 07:57:32AM +0800, Simon Jeons wrote:
>>> Hi Naoya,
>>> On 02/22/2013 03:41 AM, Naoya Horiguchi wrote:
>>>> When we have a page fault for the address which is backed by a hugepage
>>>> under migration, the kernel can't wait correctly until the migration
>>>> finishes. This is because pte_offset_map_lock() can't get a correct
>>> It seems that current hugetlb_fault still wait hugetlb page under
>>> migration, how can it work without lock 2MB memory?
>> Hugetlb_fault() does call migration_entry_wait(), but returns immediately.
> Could you point out to me which code in function migration_entry_wait()
> lead to return immediately?
>
>> So page fault happens over and over again until the migration completes.
>> IOW, migration_entry_wait() is now broken for hugepage and doesn't work
>> as expected.
>>
>> Thanks,
>> Naoya

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