Re: [RFC] memory unplug v5 [1/6] migration by kernel

[Christoph Lameter <clameter@sgi.com>]

On Thu, 14 Jun 2007, KAMEZAWA Hiroyuki wrote:

> In my understanding:
> 
> PageAnon(page) checks (page->mapping & 0x1). And, as you know, page->mapping
> is not cleared even if the page is removed from rmap.

But in that case the refcount is zero. We will not migrate the page.

> My patch should be
> ==
> +	if (PageAnon(page)) {
> +		anon_vma = page_lock_anon_vma(page);
> ==
> This is my mistake.

Do not worry I make lots of mistakes.... We just need to pool our minds 
and come up with the right solution. I think this is a critical piece of 
code that needs to be right for defrag and for memory unplug.

Why do you lock the page there? Its already locked from sys_move_pages 
etc. This will make normal page migration deadlock.

Just get the anonymous vma address from the mapping like in the last 
conceptual patch that I sent you.


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