[RFC PATCH v3 3/3] io_uring: add api to set napi prefer busy poll

[Stefan Roesch <shr@devkernel.io>]

This adds an api to register and unregister the napi prefer busy poll
setting 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 |  3 ++-
 io_uring/io_uring.c           | 17 +++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 9b5c1df0d1d8..25b91a4dc103 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -490,7 +490,8 @@ enum {
 	/* register a range of fixed file slots for automatic slot allocation */
 	IORING_REGISTER_FILE_ALLOC_RANGE	= 25,
 
-	/* set/clear busy poll timeout */
+	/* set/clear busy poll settings */
+	IORING_REGISTER_NAPI_PREFER_BUSY_POLL	= 26,
 	IORING_REGISTER_NAPI_BUSY_POLL_TIMEOUT	= 27,
 
 	/* this goes last */
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index f6c9c9cbe0f8..eca9f7540123 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -4122,6 +4122,17 @@ static __cold int io_register_iowq_max_workers(struct io_ring_ctx *ctx,
 	return ret;
 }
 
+static int io_register_napi_prefer_busy_poll(struct io_ring_ctx *ctx,
+					     unsigned int prefer_napi)
+{
+#ifdef CONFIG_NET_RX_BUSY_POLL
+	WRITE_ONCE(ctx->napi_prefer_busy_poll, !!prefer_napi);
+	return 0;
+#else
+	return -EINVAL;
+#endif
+}
+
 static int io_register_napi_busy_poll_timeout(struct io_ring_ctx *ctx, unsigned int to)
 {
 #ifdef CONFIG_NET_RX_BUSY_POLL
@@ -4292,6 +4303,12 @@ 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_PREFER_BUSY_POLL:
+		ret = -EINVAL;
+		if (arg || !nr_args)
+			break;
+		ret = io_register_napi_prefer_busy_poll(ctx, nr_args);
+		break;
 	case IORING_REGISTER_NAPI_BUSY_POLL_TIMEOUT:
 		ret = -EINVAL;
 		if (arg || !nr_args)
-- 
2.30.2