io_uring: improve sqpoll event/state handling

As sqd->state changes rarely, don't check every event one by one but
look them all at once. Add a helper function. Also don't go into event
waiting sleeping with STOP flag set.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/645025f95c7eeec97f88ff497785f4f1d6f3966f.1621201931.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -6757,6 +6757,11 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
 	return submitted;
 }
 
+static inline bool io_sqd_events_pending(struct io_sq_data *sqd)
+{
+	return READ_ONCE(sqd->state);
+}
+
 static inline void io_ring_set_wakeup_flag(struct io_ring_ctx *ctx)
 {
 	/* Tell userspace we may need a wakeup call */
@@ -6815,6 +6820,24 @@ static void io_sqd_update_thread_idle(struct io_sq_data *sqd)
 	sqd->sq_thread_idle = sq_thread_idle;
 }
 
+static bool io_sqd_handle_event(struct io_sq_data *sqd)
+{
+	bool did_sig = false;
+	struct ksignal ksig;
+
+	if (test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) ||
+	    signal_pending(current)) {
+		mutex_unlock(&sqd->lock);
+		if (signal_pending(current))
+			did_sig = get_signal(&ksig);
+		cond_resched();
+		mutex_lock(&sqd->lock);
+	}
+	io_run_task_work();
+	io_run_task_work_head(&sqd->park_task_work);
+	return did_sig || test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
+}
+
 static int io_sq_thread(void *data)
 {
 	struct io_sq_data *sqd = data;
@@ -6836,29 +6859,17 @@ static int io_sq_thread(void *data)
 	/* a user may had exited before the thread started */
 	io_run_task_work_head(&sqd->park_task_work);
 
-	while (!test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state)) {
+	while (1) {
 		int ret;
 		bool cap_entries, sqt_spin, needs_sched;
 
-		if (test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) ||
-		    signal_pending(current)) {
-			bool did_sig = false;
-
-			mutex_unlock(&sqd->lock);
-			if (signal_pending(current)) {
-				struct ksignal ksig;
-
-				did_sig = get_signal(&ksig);
-			}
-			cond_resched();
-			mutex_lock(&sqd->lock);
-			io_run_task_work();
-			io_run_task_work_head(&sqd->park_task_work);
-			if (did_sig)
+		if (io_sqd_events_pending(sqd) || signal_pending(current)) {
+			if (io_sqd_handle_event(sqd))
 				break;
 			timeout = jiffies + sqd->sq_thread_idle;
 			continue;
 		}
+
 		sqt_spin = false;
 		cap_entries = !list_is_singular(&sqd->ctx_list);
 		list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
@@ -6882,7 +6893,7 @@ static int io_sq_thread(void *data)
 		}
 
 		prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
-		if (!test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state)) {
+		if (!io_sqd_events_pending(sqd)) {
 			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
 				io_ring_set_wakeup_flag(ctx);