On 11/21/18 2:15 AM, Benny Halevy wrote:

quoted

+int iomap_dio_iopoll(struct kiocb *kiocb, bool spin)
+{
+	struct iomap_dio *dio = kiocb->private;
+	struct request_queue *q = READ_ONCE(dio->last_queue);
+
+	if (!q || dio->cookie == BLK_QC_T_NONE)
+		return 0;
+	return blk_poll(q, READ_ONCE(dio->cookie), spin);

How about:
	blk_qc_t cookie = READ_ONCE(dio->cookie);

	if (!q || cookie == BLK_QC_T_NONE)
		return 0;
	return blk_poll(q, cookie, spin);

Is there a chance the dio->cookie in the if () condition
will be stale?

I've rewritten this one, more importantly it needs to guard against
submission by ensuring that 'dio' is valid.

-- 
Jens Axboe