Re: [PATCH 04/14] mm,migration: Allow the migration of PageSwapCache pages

[Rik van Riel]

On 04/24/2010 07:59 AM, Mel Gorman wrote:
> On Sat, Apr 24, 2010 at 01:13:40PM +0200, Andrea Arcangeli wrote:

> > Also keep in mind expand_downwards which also adjusts
> > vm_start/vm_pgoff the same way (and without mmap_sem write mode).
>
> Will keep it in mind. It's taking the anon_vma lock but once again,
> there might be more than one anon_vma to worry about and the proper
> locking still isn't massively clear to me.

The locking for the anon_vma_chain->same_vma list is
essentially the same as what was used before in mmap
and anon_vma_prepare.

Either the mmap_sem is held for write, or the mmap_sem
is held for reading and the page_table_lock is held.

What exactly is the problem that migration is seeing?

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