powerpc/mm: Only check for _PAGE_PRESENT in set_pte/pmd functions

We want to make sure we don't use these function when updating a pte
or pmd entry that have a valid hpte entry, because these functions
don't invalidate them. So limit the check to _PAGE_PRESENT bit.
Numafault core changes use these functions for updating _PAGE_NUMA bits.
That should be ok because when _PAGE_NUMA is set we can be sure that
hpte entries are not present.
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/mm/pgtable.c

@@ -174,7 +174,7 @@ void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
 		pte_t pte)
 {
 #ifdef CONFIG_DEBUG_VM
-	WARN_ON(pte_present(*ptep));
+	WARN_ON(pte_val(*ptep) & _PAGE_PRESENT);
 #endif
 	/* Note: mm->context.id might not yet have been assigned as
 	 * this context might not have been activated yet when this

arch/powerpc/mm/pgtable_64.c

@@ -687,7 +687,7 @@ void set_pmd_at(struct mm_struct *mm, unsigned long addr,
 		pmd_t *pmdp, pmd_t pmd)
 {
 #ifdef CONFIG_DEBUG_VM
-	WARN_ON(!pmd_none(*pmdp));
+	WARN_ON(pmd_val(*pmdp) & _PAGE_PRESENT);
 	assert_spin_locked(&mm->page_table_lock);
 	WARN_ON(!pmd_trans_huge(pmd));
 #endif