io_uring: don't arm a timeout through work.func

Remove io_link_work_cb() -- the last custom work.func.
Not the prettiest thing, but works. Instead of queueing a linked timeout
in io_link_work_cb() mark a request with REQ_F_QUEUE_TIMEOUT and do
enqueueing based on the flag in io_wq_submit_work().
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -541,6 +541,7 @@ enum {
 	REQ_F_POLLED_BIT,
 	REQ_F_BUFFER_SELECTED_BIT,
 	REQ_F_NO_FILE_TABLE_BIT,
+	REQ_F_QUEUE_TIMEOUT_BIT,
 
 	/* not a real bit, just to check we're not overflowing the space */
 	__REQ_F_LAST_BIT,
@@ -596,6 +597,8 @@ enum {
 	REQ_F_BUFFER_SELECTED	= BIT(REQ_F_BUFFER_SELECTED_BIT),
 	/* doesn't need file table for this request */
 	REQ_F_NO_FILE_TABLE	= BIT(REQ_F_NO_FILE_TABLE_BIT),
+	/* needs to queue linked timeout */
+	REQ_F_QUEUE_TIMEOUT	= BIT(REQ_F_QUEUE_TIMEOUT_BIT),
 };
 
 struct async_poll {
@@ -1580,16 +1583,6 @@ static void io_free_req(struct io_kiocb *req)
 		io_queue_async_work(nxt);
 }
 
-static void io_link_work_cb(struct io_wq_work **workptr)
-{
-	struct io_kiocb *req = container_of(*workptr, struct io_kiocb, work);
-	struct io_kiocb *link;
-
-	link = list_first_entry(&req->link_list, struct io_kiocb, link_list);
-	io_queue_linked_timeout(link);
-	io_wq_submit_work(workptr);
-}
-
 static void io_wq_assign_next(struct io_wq_work **workptr, struct io_kiocb *nxt)
 {
 	struct io_kiocb *link;
@@ -1601,7 +1594,7 @@ static void io_wq_assign_next(struct io_wq_work **workptr, struct io_kiocb *nxt)
 	*workptr = &nxt->work;
 	link = io_prep_linked_timeout(nxt);
 	if (link)
-		nxt->work.func = io_link_work_cb;
+		nxt->flags |= REQ_F_QUEUE_TIMEOUT;
 }
 
 /*
@@ -5291,12 +5284,26 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 	return 0;
 }
 
+static void io_arm_async_linked_timeout(struct io_kiocb *req)
+{
+	struct io_kiocb *link;
+
+	/* link head's timeout is queued in io_queue_async_work() */
+	if (!(req->flags & REQ_F_QUEUE_TIMEOUT))
+		return;
+
+	link = list_first_entry(&req->link_list, struct io_kiocb, link_list);
+	io_queue_linked_timeout(link);
+}
+
 static void io_wq_submit_work(struct io_wq_work **workptr)
 {
 	struct io_wq_work *work = *workptr;
 	struct io_kiocb *req = container_of(work, struct io_kiocb, work);
 	int ret = 0;
 
+	io_arm_async_linked_timeout(req);
+
 	/* if NO_CANCEL is set, we must still run the work */
 	if ((work->flags & (IO_WQ_WORK_CANCEL|IO_WQ_WORK_NO_CANCEL)) ==
 				IO_WQ_WORK_CANCEL) {