io_uring: inline ->registered_rings

There can be only 16 registered rings, no need to allocate an array for
them separately but store it in tctx.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/495f0b953c87994dd9e13de2134019054fa5830d.1655310733.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/tctx.c

@@ -53,7 +53,6 @@ void __io_uring_free(struct task_struct *tsk)
 	WARN_ON_ONCE(tctx->io_wq);
 	WARN_ON_ONCE(tctx->cached_refs);
 
-	kfree(tctx->registered_rings);
 	percpu_counter_destroy(&tctx->inflight);
 	kfree(tctx);
 	tsk->io_uring = NULL;
@@ -69,16 +68,8 @@ __cold int io_uring_alloc_task_context(struct task_struct *task,
 	if (unlikely(!tctx))
 		return -ENOMEM;
 
-	tctx->registered_rings = kcalloc(IO_RINGFD_REG_MAX,
-					 sizeof(struct file *), GFP_KERNEL);
-	if (unlikely(!tctx->registered_rings)) {
-		kfree(tctx);
-		return -ENOMEM;
-	}
-
 	ret = percpu_counter_init(&tctx->inflight, 0, GFP_KERNEL);
 	if (unlikely(ret)) {
-		kfree(tctx->registered_rings);
 		kfree(tctx);
 		return ret;
 	}
@@ -87,7 +78,6 @@ __cold int io_uring_alloc_task_context(struct task_struct *task,
 	if (IS_ERR(tctx->io_wq)) {
 		ret = PTR_ERR(tctx->io_wq);
 		percpu_counter_destroy(&tctx->inflight);
-		kfree(tctx->registered_rings);
 		kfree(tctx);
 		return ret;
 	}

io_uring/tctx.h

@@ -20,8 +20,9 @@ struct io_uring_task {
 	struct io_wq_work_list	task_list;
 	struct io_wq_work_list	prio_task_list;
 	struct callback_head	task_work;
-	struct file		**registered_rings;
 	bool			task_running;
+
+	struct file		*registered_rings[IO_RINGFD_REG_MAX];
 };
 
 struct io_tctx_node {