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

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Message-ID: <514A4815.4040206@gmail.com>
Date:	Thu, 21 Mar 2013 07:36:53 +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()

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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