[PATCH kernel] powerpc/iommu: Do not call PageTransHuge() on tail pages

[Michael Ellerman]

Alexey Kardashevskiy <aik at ozlabs.ru> writes:

> The CMA pages migration code does not support compound pages at
> the moment so it performs few tests before proceeding to actual page
> migration.
>
> One of the tests - PageTransHuge() - has VM_BUG_ON_PAGE(PageTail()) as
> it should be called on head pages. Since we also test for PageCompound(),
> and it contains PageTail(), we can simply move PageCompound() in front
> of PageTransHuge() and therefore avoid possible VM_BUG_ON_PAGE.
>
> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
> ---
>
> Some of actual POWER8 systems do crash on that BUG_ON.

So this is:

Fixes: 2e5bbb5461f1 ("KVM: PPC: Book3S HV: Migrate pinned pages out of CMA")

And therefore:

Cc: stable at vger.kernel.org # v4.9+

?

cheers