usb: gadget: f_fs: use io_data->status consistently

Commit fb1f16d7 ("usb: gadget: f_fs: change ep->status safe in
ffs_epfile_io()") added a new ffs_io_data::status field to fix lifetime
issues in synchronous requests.

While there are no similar lifetime issues for asynchronous requests
(the separate ep member in ffs_io_data avoids them) using the status
field means the USB request can be freed earlier and that there is more
consistency between the synchronous and asynchronous I/O paths.

Cc: Linyu Yuan <quic_linyyuan@quicinc.com>
Signed-off-by: John Keeping <john@metanate.com>
Reviewed-by: Linyu Yuan <quic_linyyuan@quicinc.com>
Link: https://lore.kernel.org/r/20221124170430.3998755-1-john@metanate.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/f_fs.c

@@ -825,8 +825,7 @@ static void ffs_user_copy_worker(struct work_struct *work)
 {
 	struct ffs_io_data *io_data = container_of(work, struct ffs_io_data,
 						   work);
-	int ret = io_data->req->status ? io_data->req->status :
-					 io_data->req->actual;
+	int ret = io_data->status;
 	bool kiocb_has_eventfd = io_data->kiocb->ki_flags & IOCB_EVENTFD;
 
 	if (io_data->read && ret > 0) {
@@ -840,8 +839,6 @@ static void ffs_user_copy_worker(struct work_struct *work)
 	if (io_data->ffs->ffs_eventfd && !kiocb_has_eventfd)
 		eventfd_signal(io_data->ffs->ffs_eventfd, 1);
 
-	usb_ep_free_request(io_data->ep, io_data->req);
-
 	if (io_data->read)
 		kfree(io_data->to_free);
 	ffs_free_buffer(io_data);
@@ -856,6 +853,9 @@ static void ffs_epfile_async_io_complete(struct usb_ep *_ep,
 
 	ENTER();
 
+	io_data->status = req->status ? req->status : req->actual;
+	usb_ep_free_request(_ep, req);
+
 	INIT_WORK(&io_data->work, ffs_user_copy_worker);
 	queue_work(ffs->io_completion_wq, &io_data->work);
 }