diff --git a/fs/namespace.c b/fs/namespace.c
index bae0e95b3713a3bf143754a523f603a5a330b8ab..32a0b9146757e57c800dc4297b35a5fd12ca9ff1 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3075,7 +3075,7 @@ static void shrink_submounts(struct mount *mnt)
 void *copy_mount_options(const void __user * data)
 {
 	char *copy;
-	unsigned size;
+	unsigned left, offset;
 
 	if (!data)
 		return NULL;
@@ -3084,16 +3084,27 @@ void *copy_mount_options(const void __user * data)
 	if (!copy)
 		return ERR_PTR(-ENOMEM);
 
-	size = PAGE_SIZE - offset_in_page(data);
+	left = copy_from_user(copy, data, PAGE_SIZE);
 
-	if (copy_from_user(copy, data, size)) {
+	/*
+	 * Not all architectures have an exact copy_from_user(). Resort to
+	 * byte at a time.
+	 */
+	offset = PAGE_SIZE - left;
+	while (left) {
+		char c;
+		if (get_user(c, (const char __user *)data + offset))
+			break;
+		copy[offset] = c;
+		left--;
+		offset++;
+	}
+
+	if (left == PAGE_SIZE) {
 		kfree(copy);
 		return ERR_PTR(-EFAULT);
 	}
-	if (size != PAGE_SIZE) {
-		if (copy_from_user(copy + size, data + size, PAGE_SIZE - size))
-			memset(copy + size, 0, PAGE_SIZE - size);
-	}
+
 	return copy;
 }