x86: stricter check in follow_huge_addr()

The first page of the compound page is determined in follow_huge_addr()
but then PageCompound() only checks if the page is part of a compound page.
PageHead() allows checking if this is indeed the first page of the
compound.

Cc: Jeremy Fitzhardinge <[e-mail]>
Signed-off-by: Christoph Lameter <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/mm/hugetlbpage.c

···
 
 	page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
 
-	WARN_ON(!PageCompound(page));
+	WARN_ON(!PageHead(page));
 
 	return page;
 }