problem in follow_hugetlb_page on ppc64 architecture with get_user_pages

[Christoph Raisch]

Hello,
if get_user_pages is used on a hugetlb vma, and there was no previous write
to the pages,
follow_hugetlb_page will call
ret = hugetlb_fault(mm, vma, vaddr, 0),
although the page should be used for write access in get_user_pages.

We currently see this when testing Infiniband on ppc64 with ehca +
hugetlbfs.
>From reading the code this should also be an issue on other architectures.
Roland, Adam, are you aware of anything in this area with mellanox
Infiniband cards or other usages with I/O adapters?

Gruss / Regards
Christoph R. + Nam Ng.


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