Re: [PATCH 1/9] migrate: add migrate_entry_wait_huge()

From: Naoya Horiguchi
Date: Wed Mar 20 2013 - 17:53:41 EST

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.
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.

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