powerpc: is_hugepage_only_range() must account for both 4kB and 64kB slices

powerpc: is_hugepage_only_range() must account for both 4kB and 64kB slices

The subpage_prot syscall fails on second and subsequent calls for a given
region, because is_hugepage_only_range() is mis-identifying the 4 kB
slices when the process has a 64 kB page size.
Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/mm/slice.c

@@ -710,9 +710,18 @@ int is_hugepage_only_range(struct mm_struct *mm, unsigned long addr,
 			   unsigned long len)
 {
 	struct slice_mask mask, available;
+	unsigned int psize = mm->context.user_psize;
 
 	mask = slice_range_to_mask(addr, len);
-	available = slice_mask_for_size(mm, mm->context.user_psize);
+	available = slice_mask_for_size(mm, psize);
+#ifdef CONFIG_PPC_64K_PAGES
+	/* We need to account for 4k slices too */
+	if (psize == MMU_PAGE_64K) {
+		struct slice_mask compat_mask;
+		compat_mask = slice_mask_for_size(mm, MMU_PAGE_4K);
+		or_mask(available, compat_mask);
+	}
+#endif
 
 #if 0 /* too verbose */
 	slice_dbg("is_hugepage_only_range(mm=%p, addr=%lx, len=%lx)\n",