io_uring/tctx: have io_uring_alloc_task_context() return tctx

Instead of having io_uring_alloc_task_context() return an int and
assign tsk->io_uring, just have it return the task context directly.
This enables cleaner error handling in callers, which may have
failure points post calling io_uring_alloc_task_context().

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

io_uring/sqpoll.c

@@ -458,6 +458,7 @@ __cold int io_sq_offload_create(struct io_ring_ctx *ctx,
 			return -EINVAL;
 	}
 	if (ctx->flags & IORING_SETUP_SQPOLL) {
+		struct io_uring_task *tctx;
 		struct task_struct *tsk;
 		struct io_sq_data *sqd;
 		bool attached;
@@ -524,8 +525,13 @@ __cold int io_sq_offload_create(struct io_ring_ctx *ctx,
 		rcu_assign_pointer(sqd->thread, tsk);
 		mutex_unlock(&sqd->lock);
 
+		ret = 0;
 		get_task_struct(tsk);
-		ret = io_uring_alloc_task_context(tsk, ctx);
+		tctx = io_uring_alloc_task_context(tsk, ctx);
+		if (!IS_ERR(tctx))
+			tsk->io_uring = tctx;
+		else
+			ret = PTR_ERR(tctx);
 		wake_up_new_task(tsk);
 		if (ret)
 			goto err;

io_uring/tctx.c

@@ -74,39 +74,38 @@ void __io_uring_free(struct task_struct *tsk)
 	}
 }
 
-__cold int io_uring_alloc_task_context(struct task_struct *task,
-				       struct io_ring_ctx *ctx)
+__cold struct io_uring_task *io_uring_alloc_task_context(struct task_struct *task,
+							struct io_ring_ctx *ctx)
 {
 	struct io_uring_task *tctx;
 	int ret;
 
 	tctx = kzalloc_obj(*tctx);
 	if (unlikely(!tctx))
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 
 	ret = percpu_counter_init(&tctx->inflight, 0, GFP_KERNEL);
 	if (unlikely(ret)) {
 		kfree(tctx);
-		return ret;
+		return ERR_PTR(ret);
 	}
 
 	tctx->io_wq = io_init_wq_offload(ctx, task);
 	if (IS_ERR(tctx->io_wq)) {
 		ret = PTR_ERR(tctx->io_wq);
 		percpu_counter_destroy(&tctx->inflight);
 		kfree(tctx);
-		return ret;
+		return ERR_PTR(ret);
 	}
 
 	tctx->task = task;
 	xa_init(&tctx->xa);
 	init_waitqueue_head(&tctx->wait);
 	atomic_set(&tctx->in_cancel, 0);
 	atomic_set(&tctx->inflight_tracked, 0);
-	task->io_uring = tctx;
 	init_llist_head(&tctx->task_list);
 	init_task_work(&tctx->task_work, tctx_task_work);
-	return 0;
+	return tctx;
 }
 
 int __io_uring_add_tctx_node(struct io_ring_ctx *ctx)
@@ -116,11 +115,11 @@ int __io_uring_add_tctx_node(struct io_ring_ctx *ctx)
 	int ret;
 
 	if (unlikely(!tctx)) {
-		ret = io_uring_alloc_task_context(current, ctx);
-		if (unlikely(ret))
-			return ret;
+		tctx = io_uring_alloc_task_context(current, ctx);
+		if (IS_ERR(tctx))
+			return PTR_ERR(tctx);
 
-		tctx = current->io_uring;
+		current->io_uring = tctx;
 		if (ctx->int_flags & IO_RING_F_IOWQ_LIMITS_SET) {
 			unsigned int limits[2] = { ctx->iowq_limits[0],
 						   ctx->iowq_limits[1], };

io_uring/tctx.h

@@ -6,8 +6,8 @@ struct io_tctx_node {
 	struct io_ring_ctx	*ctx;
 };
 
-int io_uring_alloc_task_context(struct task_struct *task,
-				struct io_ring_ctx *ctx);
+struct io_uring_task *io_uring_alloc_task_context(struct task_struct *task,
+						  struct io_ring_ctx *ctx);
 void io_uring_del_tctx_node(unsigned long index);
 int __io_uring_add_tctx_node(struct io_ring_ctx *ctx);
 int __io_uring_add_tctx_node_from_submit(struct io_ring_ctx *ctx);