[RFC PATCH v1 2/2] io_uring: add api to set napi busy poll timeout.

[Stefan Roesch <shr@devkernel.io>]

This adds an api to register and unregister the busy poll timeout from
liburing. To be able to use this functionality, the corresponding
liburing patch is needed.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 include/uapi/linux/io_uring.h |  4 ++++
 io_uring/io_uring.c           | 18 ++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index ab7458033ee3..48670074e1fc 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -490,6 +490,10 @@ enum {
 	/* register a range of fixed file slots for automatic slot allocation */
 	IORING_REGISTER_FILE_ALLOC_RANGE	= 25,
 
+	/* set/clear busy poll timeout */
+	IORING_REGISTER_NAPI_BUSY_POLL_TIMEOUT	= 26,
+	IORING_UNREGISTER_NAPI_BUSY_POLL_TIMEOUT= 27,
+
 	/* this goes last */
 	IORING_REGISTER_LAST
 };
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index f64ccd537d05..c3d277772ca0 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -4108,6 +4108,12 @@ static __cold int io_register_iowq_max_workers(struct io_ring_ctx *ctx,
 	return ret;
 }
 
+static int io_register_napi_busy_poll_timeout(struct io_ring_ctx *ctx, unsigned int to)
+{
+	WRITE_ONCE(ctx->napi_busy_poll_to, to);
+	return 0;
+}
+
 static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			       void __user *arg, unsigned nr_args)
 	__releases(ctx->uring_lock)
@@ -4268,6 +4274,18 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			break;
 		ret = io_register_file_alloc_range(ctx, arg);
 		break;
+	case IORING_REGISTER_NAPI_BUSY_POLL_TIMEOUT:
+		ret = -EINVAL;
+		if (arg || !nr_args)
+			break;
+		ret = io_register_napi_busy_poll_timeout(ctx, nr_args);
+		break;
+	case IORING_UNREGISTER_NAPI_BUSY_POLL_TIMEOUT:
+		ret = -EINVAL;
+		if (arg || nr_args)
+			break;
+		ret = io_register_napi_busy_poll_timeout(ctx, nr_args);
+		break;
 	default:
 		ret = -EINVAL;
 		break;
-- 
2.30.2