io_uring: optimise tctx node checks/alloc

First of all, w need to set tctx->sqpoll only when we add a new entry
into ->xa, so move it from the hot path. Also extract a hot path for
io_uring_add_task_file() as an inline helper.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -8846,10 +8846,7 @@ static void io_uring_cancel_files(struct io_ring_ctx *ctx,
 	}
 }
 
-/*
- * Note that this task has used io_uring. We use it for cancelation purposes.
- */
-static int io_uring_add_task_file(struct io_ring_ctx *ctx)
+static int __io_uring_add_task_file(struct io_ring_ctx *ctx)
 {
 	struct io_uring_task *tctx = current->io_uring;
 	struct io_tctx_node *node;
@@ -8861,10 +8858,7 @@ static int io_uring_add_task_file(struct io_ring_ctx *ctx)
 			return ret;
 		tctx = current->io_uring;
 	}
-	if (tctx->last != ctx) {
-		void *old = xa_load(&tctx->xa, (unsigned long)ctx);
-
-		if (!old) {
+	if (!xa_load(&tctx->xa, (unsigned long)ctx)) {
 		node = kmalloc(sizeof(*node), GFP_KERNEL);
 		if (!node)
 			return -ENOMEM;
@@ -8883,10 +8877,21 @@ static int io_uring_add_task_file(struct io_ring_ctx *ctx)
 		mutex_unlock(&ctx->uring_lock);
 	}
 	tctx->last = ctx;
-	}
 	return 0;
 }
 
+/*
+ * Note that this task has used io_uring. We use it for cancelation purposes.
+ */
+static inline int io_uring_add_task_file(struct io_ring_ctx *ctx)
+{
+	struct io_uring_task *tctx = current->io_uring;
+
+	if (likely(tctx && tctx->last == ctx))
+		return 0;
+	return __io_uring_add_task_file(ctx);
+}
+
 /*
  * Remove this io_uring_file -> task mapping.
  */