pstore: switch to copy_from_user()

don't bother trying to do bulk access_ok()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/pstore/ram_core.c

@@ -283,7 +283,7 @@ static int notrace persistent_ram_update_user(struct persistent_ram_zone *prz,
 	const void __user *s, unsigned int start, unsigned int count)
 {
 	struct persistent_ram_buffer *buffer = prz->buffer;
-	int ret = unlikely(__copy_from_user(buffer->data + start, s, count)) ?
+	int ret = unlikely(copy_from_user(buffer->data + start, s, count)) ?
 		-EFAULT : 0;
 	persistent_ram_update_ecc(prz, start, count);
 	return ret;
@@ -348,8 +348,6 @@ int notrace persistent_ram_write_user(struct persistent_ram_zone *prz,
 	int rem, ret = 0, c = count;
 	size_t start;
 
-	if (unlikely(!access_ok(s, count)))
-		return -EFAULT;
 	if (unlikely(c > prz->buffer_size)) {
 		s += c - prz->buffer_size;
 		c = prz->buffer_size;