[PATCH v9 3/5] io-uring: add sqpoll support for napi busy poll

[Stefan Roesch <shr@xxxxxxxxxxxx>]

This adds the sqpoll support to the io-uring napi.

Signed-off-by: Stefan Roesch <shr@xxxxxxxxxxxx>
Suggested-by: Olivier Langlois <olivier@xxxxxxxxxxxxxx>
---
 io_uring/napi.c   | 25 +++++++++++++++++++++++++
 io_uring/napi.h   |  2 ++
 io_uring/sqpoll.c |  4 ++++
 3 files changed, 31 insertions(+)

diff --git a/io_uring/napi.c b/io_uring/napi.c
index bb7d2b6b7e90..0fbdfe5eea06 100644
--- a/io_uring/napi.c
+++ b/io_uring/napi.c
@@ -240,4 +240,29 @@ void io_napi_busy_loop(struct io_ring_ctx *ctx, struct io_wait_queue *iowq)
 	}
 }
 
+/*
+ * io_napi_sqpoll_busy_poll() - busy poll loop for sqpoll
+ * @ctx: pointer to io-uring context structure
+ *
+ * Splice of the napi list and execute the napi busy poll loop.
+ */
+int io_napi_sqpoll_busy_poll(struct io_ring_ctx *ctx)
+{
+	int ret = 0;
+	LIST_HEAD(napi_list);
+
+	if (!READ_ONCE(ctx->napi_busy_poll_to))
+		return 0;
+
+	spin_lock(&ctx->napi_lock);
+	list_splice_init(&ctx->napi_list, &napi_list);
+	spin_unlock(&ctx->napi_lock);
+
+	if (__io_napi_busy_loop(&napi_list, ctx->napi_prefer_busy_poll))
+		ret = 1;
+
+	io_napi_merge_lists(ctx, &napi_list);
+	return ret;
+}
+
 #endif
diff --git a/io_uring/napi.h b/io_uring/napi.h
index 49322a16b6e5..b3455e52170c 100644
--- a/io_uring/napi.h
+++ b/io_uring/napi.h
@@ -17,6 +17,7 @@ void __io_napi_add(struct io_ring_ctx *ctx, struct file *file);
 void io_napi_adjust_timeout(struct io_ring_ctx *ctx,
 		struct io_wait_queue *iowq, struct timespec64 *ts);
 void io_napi_busy_loop(struct io_ring_ctx *ctx, struct io_wait_queue *iowq);
+int io_napi_sqpoll_busy_poll(struct io_ring_ctx *ctx);
 
 static inline bool io_napi(struct io_ring_ctx *ctx)
 {
@@ -60,6 +61,7 @@ static inline void io_napi_add(struct io_kiocb *req)
 
 #define io_napi_adjust_timeout(ctx, iowq, ts) do {} while (0)
 #define io_napi_busy_loop(ctx, iowq) do {} while (0)
+#define io_napi_sqpoll_busy_poll(ctx) (0)
 
 #endif
 
diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c
index 0119d3f1a556..b8b8cf3b6b02 100644
--- a/io_uring/sqpoll.c
+++ b/io_uring/sqpoll.c
@@ -15,6 +15,7 @@
 #include <uapi/linux/io_uring.h>
 
 #include "io_uring.h"
+#include "napi.h"
 #include "sqpoll.h"
 
 #define IORING_SQPOLL_CAP_ENTRIES_VALUE 8
@@ -193,6 +194,9 @@ static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
 			ret = io_submit_sqes(ctx, to_submit);
 		mutex_unlock(&ctx->uring_lock);
 
+		if (io_napi(ctx))
+			ret += io_napi_sqpoll_busy_poll(ctx);
+
 		if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
 			wake_up(&ctx->sqo_sq_wait);
 		if (creds)
-- 
2.30.2