io_uring/napi: clean up __io_napi_do_busy_loop

__io_napi_do_busy_loop now requires to have loop_end in its parameters.
This makes the code cleaner and also has the benefit of removing a
branch since the only caller not passing NULL for loop_end_arg is also
setting the value conditionally.

Signed-off-by: Olivier Langlois <[email protected]>
Link: https://lore.kernel.org/r/d5b9bb91b1a08fff50525e1c18d7b4709b9ca100.1728828877.git.olivier@trillion01.com
Signed-off-by: Jens Axboe <[email protected]>

Author: Olivier Langlois

io_uring/napi.c

@@ -137,15 +137,12 @@ static bool io_napi_busy_loop_should_end(void *data,
 }
 
 static bool __io_napi_do_busy_loop(struct io_ring_ctx *ctx,
+				   bool (*loop_end)(void *, unsigned long),
 				   void *loop_end_arg)
 {
 	struct io_napi_entry *e;
-	bool (*loop_end)(void *, unsigned long) = NULL;
 	bool is_stale = false;
 
-	if (loop_end_arg)
-		loop_end = io_napi_busy_loop_should_end;
-
 	list_for_each_entry_rcu(e, &ctx->napi_list, list) {
 		napi_busy_loop_rcu(e->napi_id, loop_end, loop_end_arg,
 				   ctx->napi_prefer_busy_poll, BUSY_POLL_BUDGET);
@@ -161,18 +158,22 @@ static void io_napi_blocking_busy_loop(struct io_ring_ctx *ctx,
 				       struct io_wait_queue *iowq)
 {
 	unsigned long start_time = busy_loop_current_time();
+	bool (*loop_end)(void *, unsigned long) = NULL;
 	void *loop_end_arg = NULL;
 	bool is_stale = false;
 
 	/* Singular lists use a different napi loop end check function and are
 	 * only executed once.
 	 */
-	if (list_is_singular(&ctx->napi_list))
+	if (list_is_singular(&ctx->napi_list)) {
+		loop_end = io_napi_busy_loop_should_end;
 		loop_end_arg = iowq;
+	}
 
 	scoped_guard(rcu) {
 		do {
-			is_stale = __io_napi_do_busy_loop(ctx, loop_end_arg);
+			is_stale = __io_napi_do_busy_loop(ctx, loop_end,
+							  loop_end_arg);
 		} while (!io_napi_busy_loop_should_end(iowq, start_time) &&
 			 !loop_end_arg);
 	}
@@ -308,7 +309,7 @@ int io_napi_sqpoll_busy_poll(struct io_ring_ctx *ctx)
 		return 0;
 
 	scoped_guard(rcu) {
-		is_stale = __io_napi_do_busy_loop(ctx, NULL);
+		is_stale = __io_napi_do_busy_loop(ctx, NULL, NULL);
 	}
 
 	io_napi_remove_stale(ctx, is_stale);