[PATCH 4/4] io_uring/msg_ring: improve handling of target CQE posting

[Jens Axboe <axboe@xxxxxxxxx>]

Use the exported helper for queueing task_work, rather than rolling our
own.

This improves peak performance of message passing by about 5x in some
basic testing, with 2 threads just sending messages to each other.
Before this change, it was capped at around 700K/sec, with the change
it's at over 4M/sec.

Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
 io_uring/msg_ring.c | 26 +++++++-------------------
 1 file changed, 7 insertions(+), 19 deletions(-)

diff --git a/io_uring/msg_ring.c b/io_uring/msg_ring.c
index 9023b39fecef..3e1b9158798e 100644
--- a/io_uring/msg_ring.c
+++ b/io_uring/msg_ring.c
@@ -13,7 +13,6 @@
 #include "filetable.h"
 #include "msg_ring.h"
 
-
 /* All valid masks for MSG_RING */
 #define IORING_MSG_RING_MASK		(IORING_MSG_RING_CQE_SKIP | \
 					IORING_MSG_RING_FLAGS_PASS)
@@ -21,7 +20,6 @@
 struct io_msg {
 	struct file			*file;
 	struct file			*src_file;
-	struct callback_head		tw;
 	u64 user_data;
 	u32 len;
 	u32 cmd;
@@ -73,26 +71,18 @@ static inline bool io_msg_need_remote(struct io_ring_ctx *target_ctx)
 	return current != target_ctx->submitter_task;
 }
 
-static int io_msg_exec_remote(struct io_kiocb *req, task_work_func_t func)
+static int io_msg_exec_remote(struct io_kiocb *req, io_req_tw_func_t func)
 {
 	struct io_ring_ctx *ctx = req->file->private_data;
-	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
-	struct task_struct *task = READ_ONCE(ctx->submitter_task);
-
-	if (unlikely(!task))
-		return -EOWNERDEAD;
-
-	init_task_work(&msg->tw, func);
-	if (task_work_add(ctx->submitter_task, &msg->tw, TWA_SIGNAL))
-		return -EOWNERDEAD;
 
+	req->io_task_work.func = func;
+	io_req_task_work_add_remote(req, ctx, IOU_F_TWQ_LAZY_WAKE);
 	return IOU_ISSUE_SKIP_COMPLETE;
 }
 
-static void io_msg_tw_complete(struct callback_head *head)
+static void io_msg_tw_complete(struct io_kiocb *req, struct io_tw_state *ts)
 {
-	struct io_msg *msg = container_of(head, struct io_msg, tw);
-	struct io_kiocb *req = cmd_to_io_kiocb(msg);
+	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
 	struct io_ring_ctx *target_ctx = req->file->private_data;
 	int ret = 0;
 
@@ -215,14 +205,12 @@ static int io_msg_install_complete(struct io_kiocb *req, unsigned int issue_flag
 	return ret;
 }
 
-static void io_msg_tw_fd_complete(struct callback_head *head)
+static void io_msg_tw_fd_complete(struct io_kiocb *req, struct io_tw_state *ts)
 {
-	struct io_msg *msg = container_of(head, struct io_msg, tw);
-	struct io_kiocb *req = cmd_to_io_kiocb(msg);
 	int ret = -EOWNERDEAD;
 
 	if (!(current->flags & PF_EXITING))
-		ret = io_msg_install_complete(req, IO_URING_F_UNLOCKED);
+		ret = __io_msg_install_complete(req);
 	if (ret < 0)
 		req_set_fail(req);
 	io_req_queue_tw_complete(req, ret);
-- 
2.43.0