io_uring: simplify waking sqo_sq_wait

Going through submission in __io_sq_thread() and still having a full SQ
is rather unexpected, so remove a check for SQ fullness and just wake up
whoever wait on sqo_sq_wait. Also skip if it doesn't do submission in
the first place, likely may to happen for SQPOLL sharing and/or IOPOLL.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/e2e91751e87b1a39f8d63ef884aaff578123f61e.1621201931.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -6801,10 +6801,10 @@ static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
 		    !(ctx->flags & IORING_SETUP_R_DISABLED))
 			ret = io_submit_sqes(ctx, to_submit);
 		mutex_unlock(&ctx->uring_lock);
-	}
 
-	if (!io_sqring_full(ctx) && wq_has_sleeper(&ctx->sqo_sq_wait))
-		wake_up(&ctx->sqo_sq_wait);
+		if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
+			wake_up(&ctx->sqo_sq_wait);
+	}
 
 	return ret;
 }