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xen-devel
Re: [Xen-devel] [RFC] linux: add p[mug]d_clear_full() accessors
>> One question though - in our 2.6.23 merge (where pv-ops-Xen's
>> PG_pinned appeared as an alias of PG_owner_priv_1, and where
>> PG_arch_1 got assigned a meaning for native x86, so PG_pinned
>> for the traditional patches needed to change anyway) I intentionally
>> didn't follow pv-ops for our patches, since PG_pinned is among the
>> flags bad_page() checks for (in the XenSource tree, and I think this
>> should really also be done in upstream Linux), and hence re-using
>> the bit here would change behavior for other parts of the kernel.
>
>I don't think so. So long as its clear by the time you free the page,
>it doesn't matter how it gets used in the meantime (after all, you
>should never free a pinned pagetable page).
But isn't that one of the purposes of those page flags checks - checking
whether e.g. a page may validly get freed (free_pages_check())? All
of bad_page(), free_pages_check(), and prep_new_page() currently
add PG_pinned into the set of flags cleared/checked, and I continue to
think that that is the right thing to do.
Jan
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