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SubjectRe: [v2.6.26] what's brewing in x86.git for v2.6.26
Date
Hi,

Andrew Morton <akpm@linux-foundation.org> writes:

> - extensive damage to the page-flags patches
>
> Did you check that all architectures and configurations still have
> sufficient page flags for us to be able to consume another one for
> kmemcheck? The MM developers have put much, much effort into avoiding
> running out of flags over numerous years and afaik none of them even know
> that this debug feature is using one of the few remaining ones.
>
> What do we do when we run out?

Would it be feasible to add another unsigned long to struct page? I
mean, extending such a common structure always sucks, but for
emergency...

#define PageFoobar(page) test_bit(PG_foobar, &(page)->flags2)

Of course the essential core flags should always be in ->flags but
perhaps we could have a symbol CONFIG_NEED_EXTRA_PAGE_FLAGS that gets
selected by kmemcheck (and other candidates that are unlikely to be
enabled most of the time) and then #ifndef ->flags2 out.

Hannes


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