io_uring: remove double poll on poll update

Before updating a poll request we should remove it from poll queues,
including the double poll entry.

Fixes: b69de28 ("io_uring: allow events and user_data update of running poll requests")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ac39e7f80152613603b8a6cc29a2b6063ac2434f.1639605189.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -5980,6 +5980,7 @@ static int io_poll_update(struct io_kiocb *req, unsigned int issue_flags)
 	 * update those. For multishot, if we're racing with completion, just
 	 * let completion re-add it.
 	 */
+	io_poll_remove_double(preq);
 	completing = !__io_poll_remove_one(preq, &preq->poll, false);
 	if (completing && (preq->poll.events & EPOLLONESHOT)) {
 		ret = -EALREADY;