Benjamin Herrenschmidt [off-list ref] writes:

On Tue, 2014-07-15 at 20:22 +0530, Aneesh Kumar K.V wrote:

quoted

If we changed base page size of the segment, either via sub_page_protect
or via remap_4k_pfn, we do a demote_segment which doesn't flush the hash
table entries. We do that when inserting a new hash pte by checking the
_PAGE_COMBO flag. We missed to do that when inserting hash for a new 16MB
page. Add the same. This patch mark the 4k base page size 16MB hugepage
via _PAGE_COMBO.

please improve the above, I don't understand it.

I have reworked this patch and will send an updated version. We also
need to handle _PAGE_COMBO condition on hugepage_flush. I will add more
comments in the next update.

-aneesh