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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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