Re: [PATCH 01/15] mm: poison struct page for ptlock

[Hugh Dickins]

On Wed, 9 Nov 2005, Andrew Morton wrote:
> 
> It does everything we want.

I don't think so: the union leaves us just as vulnerable to some
subsystem using fields of the other half of the union, doesn't it?

Which is not really a problem, but is a part of what's worrying you.

> Of course, it would be nice to retain 2.95.x support.  The reviled
> page_private(() would help us do that.  But the now-to-be-reviled
> page_mapping() does extraneous stuff, and we'd need a ton of page_lru()'s.
> 
> So it'd be a big patch, converting page->lru to page->u.s.lru in lots of
> places.
> 
> But I think either a big patch or 2.95.x abandonment is preferable to this
> approach.

Hmm, that's a pity.

Hugh
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