Commit fb1f16d74e26 ("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>
---
 drivers/usb/gadget/function/f_fs.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 73dc10a77cde..1221f0d1b1a9 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/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);
 }
-- 
2.38.1

Reviewed-by: Linyu Yuan <quic_linyyuan@quicinc.com>


On 11/25/2022 1:04 AM, John Keeping wrote:
> Commit fb1f16d74e26 ("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>
> ---
>   drivers/usb/gadget/function/f_fs.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index 73dc10a77cde..1221f0d1b1a9 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/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);
>   }