io_uring: Add to traces the req pointer when available

The req pointer uniquely identify a specific request.
Having it in traces can provide valuable insights that is not possible
to have if the calling process is reusing the same user_data value.
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Olivier Langlois <olivier@trillion01.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -5073,7 +5073,7 @@ static void io_async_task_func(struct callback_head *cb)
 	struct async_poll *apoll = req->apoll;
 	struct io_ring_ctx *ctx = req->ctx;
 
-	trace_io_uring_task_run(req->ctx, req->opcode, req->user_data);
+	trace_io_uring_task_run(req->ctx, req, req->opcode, req->user_data);
 
 	if (io_poll_rewait(req, &apoll->poll)) {
 		spin_unlock_irq(&ctx->completion_lock);
@@ -5206,8 +5206,8 @@ static bool io_arm_poll_handler(struct io_kiocb *req)
 		return false;
 	}
 	spin_unlock_irq(&ctx->completion_lock);
-	trace_io_uring_poll_arm(ctx, req->opcode, req->user_data, mask,
-					apoll->poll.events);
+	trace_io_uring_poll_arm(ctx, req, req->opcode, req->user_data,
+				mask, apoll->poll.events);
 	return true;
 }
 
@@ -6604,8 +6604,9 @@ static int io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
 		goto fail_req;
 
 	/* don't need @sqe from now on */
-	trace_io_uring_submit_sqe(ctx, req->opcode, req->user_data,
-				true, ctx->flags & IORING_SETUP_SQPOLL);
+	trace_io_uring_submit_sqe(ctx, req, req->opcode, req->user_data,
+				  req->flags, true,
+				  ctx->flags & IORING_SETUP_SQPOLL);
 
 	/*
 	 * If we already have a head request, queue this one for async

include/trace/events/io_uring.h

@@ -323,8 +323,10 @@ TRACE_EVENT(io_uring_complete,
  * io_uring_submit_sqe - called before submitting one SQE
  *
  * @ctx:		pointer to a ring context structure
+ * @req:		pointer to a submitted request
  * @opcode:		opcode of request
  * @user_data:		user data associated with the request
+ * @flags		request flags
  * @force_nonblock:	whether a context blocking or not
  * @sq_thread:		true if sq_thread has submitted this SQE
  *
@@ -333,41 +335,60 @@ TRACE_EVENT(io_uring_complete,
  */
 TRACE_EVENT(io_uring_submit_sqe,
 
-	TP_PROTO(void *ctx, u8 opcode, u64 user_data, bool force_nonblock,
-		 bool sq_thread),
+	TP_PROTO(void *ctx, void *req, u8 opcode, u64 user_data, u32 flags,
+		 bool force_nonblock, bool sq_thread),
 
-	TP_ARGS(ctx, opcode, user_data, force_nonblock, sq_thread),
+	TP_ARGS(ctx, req, opcode, user_data, flags, force_nonblock, sq_thread),
 
 	TP_STRUCT__entry (
 		__field(  void *,	ctx		)
+		__field(  void *,	req		)
 		__field(  u8,		opcode		)
 		__field(  u64,		user_data	)
+		__field(  u32,		flags		)
 		__field(  bool,		force_nonblock	)
 		__field(  bool,		sq_thread	)
 	),
 
 	TP_fast_assign(
 		__entry->ctx		= ctx;
+		__entry->req		= req;
 		__entry->opcode		= opcode;
 		__entry->user_data	= user_data;
+		__entry->flags		= flags;
 		__entry->force_nonblock	= force_nonblock;
 		__entry->sq_thread	= sq_thread;
 	),
 
-	TP_printk("ring %p, op %d, data 0x%llx, non block %d, sq_thread %d",
-			  __entry->ctx, __entry->opcode,
-			  (unsigned long long) __entry->user_data,
-			  __entry->force_nonblock, __entry->sq_thread)
+	TP_printk("ring %p, req %p, op %d, data 0x%llx, flags %u, "
+		  "non block %d, sq_thread %d", __entry->ctx, __entry->req,
+		  __entry->opcode, (unsigned long long)__entry->user_data,
+		  __entry->flags, __entry->force_nonblock, __entry->sq_thread)
 );
 
+/*
+ * io_uring_poll_arm - called after arming a poll wait if successful
+ *
+ * @ctx:		pointer to a ring context structure
+ * @req:		pointer to the armed request
+ * @opcode:		opcode of request
+ * @user_data:		user data associated with the request
+ * @mask:		request poll events mask
+ * @events:		registered events of interest
+ *
+ * Allows to track which fds are waiting for and what are the events of
+ * interest.
+ */
 TRACE_EVENT(io_uring_poll_arm,
 
-	TP_PROTO(void *ctx, u8 opcode, u64 user_data, int mask, int events),
+	TP_PROTO(void *ctx, void *req, u8 opcode, u64 user_data,
+		 int mask, int events),
 
-	TP_ARGS(ctx, opcode, user_data, mask, events),
+	TP_ARGS(ctx, req, opcode, user_data, mask, events),
 
 	TP_STRUCT__entry (
 		__field(  void *,	ctx		)
+		__field(  void *,	req		)
 		__field(  u8,		opcode		)
 		__field(  u64,		user_data	)
 		__field(  int,		mask		)
@@ -376,16 +397,17 @@ TRACE_EVENT(io_uring_poll_arm,
 
 	TP_fast_assign(
 		__entry->ctx		= ctx;
+		__entry->req		= req;
 		__entry->opcode		= opcode;
 		__entry->user_data	= user_data;
 		__entry->mask		= mask;
 		__entry->events		= events;
 	),
 
-	TP_printk("ring %p, op %d, data 0x%llx, mask 0x%x, events 0x%x",
-			  __entry->ctx, __entry->opcode,
-			  (unsigned long long) __entry->user_data,
-			  __entry->mask, __entry->events)
+	TP_printk("ring %p, req %p, op %d, data 0x%llx, mask 0x%x, events 0x%x",
+		  __entry->ctx, __entry->req, __entry->opcode,
+		  (unsigned long long) __entry->user_data,
+		  __entry->mask, __entry->events)
 );
 
 TRACE_EVENT(io_uring_poll_wake,
@@ -440,27 +462,40 @@ TRACE_EVENT(io_uring_task_add,
 			  __entry->mask)
 );
 
+/*
+ * io_uring_task_run - called when task_work_run() executes the poll events
+ *                     notification callbacks
+ *
+ * @ctx:		pointer to a ring context structure
+ * @req:		pointer to the armed request
+ * @opcode:		opcode of request
+ * @user_data:		user data associated with the request
+ *
+ * Allows to track when notified poll events are processed
+ */
 TRACE_EVENT(io_uring_task_run,
 
-	TP_PROTO(void *ctx, u8 opcode, u64 user_data),
+	TP_PROTO(void *ctx, void *req, u8 opcode, u64 user_data),
 
-	TP_ARGS(ctx, opcode, user_data),
+	TP_ARGS(ctx, req, opcode, user_data),
 
 	TP_STRUCT__entry (
 		__field(  void *,	ctx		)
+		__field(  void *,	req		)
 		__field(  u8,		opcode		)
 		__field(  u64,		user_data	)
 	),
 
 	TP_fast_assign(
 		__entry->ctx		= ctx;
+		__entry->req		= req;
 		__entry->opcode		= opcode;
 		__entry->user_data	= user_data;
 	),
 
-	TP_printk("ring %p, op %d, data 0x%llx",
-			  __entry->ctx, __entry->opcode,
-			  (unsigned long long) __entry->user_data)
+	TP_printk("ring %p, req %p, op %d, data 0x%llx",
+		  __entry->ctx, __entry->req, __entry->opcode,
+		  (unsigned long long) __entry->user_data)
 );
 
 #endif /* _TRACE_IO_URING_H */