On Tue, 2017-03-28 at 16:25 +1100, Alexey Kardashevskiy wrote:

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 <redacted>
---

The fix looks reasonable to me. I suspect the checks can be simplified
and we can support split and move of THP in the future.

For now, looks good

Acked-by: Balbir Singh <bsingharora@gmail.com>