io_uring: introduce io_has_work

This will be used later to know if the ring has outstanding work. Right
now just if there is overflow CQEs to copy to the main CQE ring, but later
will include deferred tasks

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220830125013.570060-3-dylany@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.c

@@ -2146,6 +2146,11 @@ struct io_wait_queue {
 	unsigned nr_timeouts;
 };
 
+static inline bool io_has_work(struct io_ring_ctx *ctx)
+{
+	return test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq);
+}
+
 static inline bool io_should_wake(struct io_wait_queue *iowq)
 {
 	struct io_ring_ctx *ctx = iowq->ctx;
@@ -2164,13 +2169,13 @@ static int io_wake_function(struct wait_queue_entry *curr, unsigned int mode,
 {
 	struct io_wait_queue *iowq = container_of(curr, struct io_wait_queue,
 							wq);
+	struct io_ring_ctx *ctx = iowq->ctx;
 
 	/*
 	 * Cannot safely flush overflowed CQEs from here, ensure we wake up
 	 * the task, and the next invocation will do it.
 	 */
-	if (io_should_wake(iowq) ||
-	    test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &iowq->ctx->check_cq))
+	if (io_should_wake(iowq) || io_has_work(ctx))
 		return autoremove_wake_function(curr, mode, wake_flags, key);
 	return -1;
 }
@@ -2506,8 +2511,8 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait)
 	 * Users may get EPOLLIN meanwhile seeing nothing in cqring, this
 	 * pushs them to do the flush.
 	 */
-	if (io_cqring_events(ctx) ||
-	    test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq))
+
+	if (io_cqring_events(ctx) || io_has_work(ctx))
 		mask |= EPOLLIN | EPOLLRDNORM;
 
 	return mask;