[RFC PATCH v4 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           | 5 ++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 1a713bbafaee..b74021454bf7 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -619,7 +619,8 @@ struct io_uring_buf_reg {
 /* argument for IORING_(UN)REGISTER_NAPI */
 struct io_uring_napi {
 	__u32	busy_poll_to;
-	__u32	pad;
+	__u8    prefer_busy_poll;
+	__u8	pad[3];
 	__u64	resv;
 };
 
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index cf0e7cc8ad2e..dd903c71fa20 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -4127,6 +4127,7 @@ static int io_register_napi(struct io_ring_ctx *ctx, void __user *arg)
 #ifdef CONFIG_NET_RX_BUSY_POLL
 	const struct io_uring_napi curr = {
 		.busy_poll_to = ctx->napi_busy_poll_to,
+		.prefer_busy_poll = ctx->napi_prefer_busy_poll
 	};
 	struct io_uring_napi *napi;
 
@@ -4135,7 +4136,7 @@ static int io_register_napi(struct io_ring_ctx *ctx, void __user *arg)
 		return PTR_ERR(napi);
 
 	WRITE_ONCE(ctx->napi_busy_poll_to, napi->busy_poll_to);
-
+	WRITE_ONCE(ctx->napi_prefer_busy_poll, !!napi->prefer_busy_poll);
 	kfree(napi);
 
 	if (copy_to_user(arg, &curr, sizeof(curr)))
@@ -4152,12 +4153,14 @@ static int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg)
 #ifdef CONFIG_NET_RX_BUSY_POLL
 	const struct io_uring_napi curr = {
 		.busy_poll_to = ctx->napi_busy_poll_to,
+		.prefer_busy_poll = ctx->napi_prefer_busy_poll
 	};
 
 	if (copy_to_user(arg, &curr, sizeof(curr)))
 		return -EFAULT;
 
 	WRITE_ONCE(ctx->napi_busy_poll_to, 0);
+	WRITE_ONCE(ctx->napi_prefer_busy_poll, false);
 	return 0;
 #else
 	return -EINVAL;
-- 
2.30.2