Re: Race in new page migration code?

[Christoph Lameter <clameter@engr.sgi.com>]

On Mon, 16 Jan 2006, Hugh Dickins wrote:

> Indeed they are, at present and quite likely into posterity.  But
> they're not a common case here, and migrate_page_add now handles them
> silently, so why bother to complicate it with an unnecessary check?

check_range also is used for statistics and for checking if a range is 
policy compliant. Without that check zeropages may be counted or flagged 
as not on the right node with MPOL_MF_STRICT.

For migrate_page_add this has now simply become an optimization since
there is no WARN_ON occurring anymore.

> Or have you found the zero page mapcount distorting get_stats stats?
> If that's an issue, then better add a commented test for it there.

It also applies to the policy compliance check.

> Hmm, that battery of unusual tests at the start of migrate_page_add
> is odd: the tests don't quite match the comment, and it isn't clear
> what reasoning lies behind the comment anywa

Hmm.... Maybe better clean up the thing a bit. Will do that when I get 
back to work next week.

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