powerpc/mm/hugetlb: Fix kernel crash if we fail to allocate page table caches

We only check for hugetlb allocations, because with hugetlb we do conditional
registration. For PGD/PUD/PMD levels we register them always in
pgtable_cache_init.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/hugetlbpage.c

@@ -61,12 +61,17 @@ static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
 		num_hugepd = 1;
 	}
 
+	if (!cachep) {
+		WARN_ONCE(1, "No page table cache created for hugetlb tables");
+		return -ENOMEM;
+	}
+
 	new = kmem_cache_alloc(cachep, pgtable_gfp_flags(mm, GFP_KERNEL));
 
 	BUG_ON(pshift > HUGEPD_SHIFT_MASK);
 	BUG_ON((unsigned long)new & HUGEPD_SHIFT_MASK);
 
-	if (! new)
+	if (!new)
 		return -ENOMEM;
 
 	/*