io_uring: refactor poll update

Clean up io_poll_update() and unify cancellation paths for remove and
update.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/5937138b6265a1285220e2fab1b28132c1d73ce3.1639605189.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -5960,61 +5960,51 @@ static int io_poll_update(struct io_kiocb *req, unsigned int issue_flags)
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_kiocb *preq;
 	bool completing;
-	int ret;
+	int ret2, ret = 0;
 
 	spin_lock(&ctx->completion_lock);
 	preq = io_poll_find(ctx, req->poll_update.old_user_data, true);
 	if (!preq) {
 		ret = -ENOENT;
-		goto err;
-	}
-
-	if (!req->poll_update.update_events && !req->poll_update.update_user_data) {
-		completing = true;
-		ret = io_poll_remove_one(preq) ? 0 : -EALREADY;
-		goto err;
+fail:
+		spin_unlock(&ctx->completion_lock);
+		goto out;
 	}
-
+	io_poll_remove_double(preq);
 	/*
 	 * Don't allow racy completion with singleshot, as we cannot safely
 	 * 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;
-		goto err;
-	}
-	/* we now have a detached poll request. reissue. */
-	ret = 0;
-err:
-	if (ret < 0) {
-		spin_unlock(&ctx->completion_lock);
-		req_set_fail(req);
-		io_req_complete(req, ret);
-		return 0;
-	}
-	/* only mask one event flags, keep behavior flags */
-	if (req->poll_update.update_events) {
-		preq->poll.events &= ~0xffff;
-		preq->poll.events |= req->poll_update.events & 0xffff;
-		preq->poll.events |= IO_POLL_UNMASK;
+		goto fail;
 	}
-	if (req->poll_update.update_user_data)
-		preq->user_data = req->poll_update.new_user_data;
 	spin_unlock(&ctx->completion_lock);
 
-	/* complete update request, we're done with it */
-	io_req_complete(req, ret);
-
-	if (!completing) {
-		ret = io_poll_add(preq, issue_flags);
-		if (ret < 0) {
-			req_set_fail(preq);
-			io_req_complete(preq, ret);
+	if (req->poll_update.update_events || req->poll_update.update_user_data) {
+		/* only mask one event flags, keep behavior flags */
+		if (req->poll_update.update_events) {
+			preq->poll.events &= ~0xffff;
+			preq->poll.events |= req->poll_update.events & 0xffff;
+			preq->poll.events |= IO_POLL_UNMASK;
 		}
+		if (req->poll_update.update_user_data)
+			preq->user_data = req->poll_update.new_user_data;
+
+		ret2 = io_poll_add(preq, issue_flags);
+		/* successfully updated, don't complete poll request */
+		if (!ret2)
+			goto out;
 	}
+	req_set_fail(preq);
+	io_req_complete(preq, -ECANCELED);
+out:
+	if (ret < 0)
+		req_set_fail(req);
+	/* complete update request, we're done with it */
+	io_req_complete(req, ret);
 	return 0;
 }