[PATCH v8 5/7] 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 c9e2afae382d..038957b46a0e 100644
--- a/io_uring/napi.c
+++ b/io_uring/napi.c
@@ -278,4 +278,29 @@ void io_napi_end_busy_loop(struct io_ring_ctx *ctx, struct io_wait_queue *iowq,
 		io_napi_merge_lists(ctx, napi_list);
 }
 
+/*
+ * io_napi_sqpoll_busy_poll() - busy poll loop for sqpoll
+ * @ctx: pointer to io-uring context structure
+ * @napi_list: pointer to head of napi list
+ *
+ * Splice of the napi list and execute the napi busy poll loop.
+ */
+int io_napi_sqpoll_busy_poll(struct io_ring_ctx *ctx, struct list_head *napi_list)
+{
+	int ret = 0;
+
+	spin_lock(&ctx->napi_lock);
+	list_splice_init(&ctx->napi_list, napi_list);
+	spin_unlock(&ctx->napi_lock);
+
+	if (!list_empty(napi_list) &&
+	    READ_ONCE(ctx->napi_busy_poll_to) > 0 &&
+	    io_napi_busy_loop(napi_list, ctx->napi_prefer_busy_poll)) {
+		io_napi_merge_lists(ctx, napi_list);
+		ret = 1;
+	}
+
+	return ret;
+}
+
 #endif
diff --git a/io_uring/napi.h b/io_uring/napi.h
index 0672592cfb79..23a6df32805f 100644
--- a/io_uring/napi.h
+++ b/io_uring/napi.h
@@ -23,6 +23,7 @@ void io_napi_adjust_busy_loop_timeout(struct io_ring_ctx *ctx,
 			struct timespec64 *ts);
 void io_napi_end_busy_loop(struct io_ring_ctx *ctx, struct io_wait_queue *iowq,
 			struct list_head *napi_list);
+int io_napi_sqpoll_busy_poll(struct io_ring_ctx *ctx, struct list_head *napi_list);
 
 #else
 
@@ -43,6 +44,7 @@ static inline void io_napi_add(struct io_kiocb *req)
 #define io_napi_setup_busy_loop(ctx, iowq, napi_list) do {} while (0)
 #define io_napi_adjust_busy_loop_timeout(ctx, iowq, napi_list, ts) do {} while (0)
 #define io_napi_end_busy_loop(ctx, iowq, napi_list) do {} while (0)
+#define io_napi_sqpoll_busy_poll(ctx, napi_list) (0)
 
 #endif
 
diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c
index 0119d3f1a556..90fdbd87434a 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
@@ -168,6 +169,7 @@ static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
 {
 	unsigned int to_submit;
 	int ret = 0;
+	NAPI_LIST_HEAD(local_napi_list);
 
 	to_submit = io_sqring_entries(ctx);
 	/* if we're handling multiple rings, cap submit size for fairness */
@@ -193,6 +195,8 @@ 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);
 
+		ret += io_napi_sqpoll_busy_poll(ctx, &local_napi_list);
+
 		if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
 			wake_up(&ctx->sqo_sq_wait);
 		if (creds)
-- 
2.30.2