Re: [PATCH net 3/4] NTB: ntb_transport: Fail TX enqueue when the QP link is down

[Dave Jiang <dave.jiang@intel.com>]

On 8/16/26 10:35 PM, Koichiro Den wrote:
> Commit f195a1a6fe41 ("ntb: Drop packets when qp link is down") meant to
> make ntb_transport_tx_enqueue() drop packets submitted while the QP link
> is down, but it only returns 0 without consuming the packet. Zero means
> success by this function's contract, so ntb_netdev reports NETDEV_TX_OK
> and forgets the skb: nothing queued it, nothing frees it, and it leaks,
> one skb for every transmit racing a link-down.
> 
> Return -ENOLINK instead, restoring the contract that a non-zero return
> leaves the buffer owned by the caller. With the preceding patch,
> ntb_netdev frees the skb on non-retryable enqueue failures and returns
> NETDEV_TX_OK, so a packet racing with link-down is dropped without leaking
> or entering a busy retry loop.
> 
> Fixes: f195a1a6fe41 ("ntb: Drop packets when qp link is down")
> Cc: stable@vger.kernel.org
> Signed-off-by: Koichiro Den <den@valinux.co.jp>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> ---
>  drivers/ntb/ntb_transport.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
> index e92b96f4afad..4bdd81edcb87 100644
> --- a/drivers/ntb/ntb_transport.c
> +++ b/drivers/ntb/ntb_transport.c
> @@ -2353,9 +2353,8 @@ int ntb_transport_tx_enqueue(struct ntb_transport_qp *qp, void *cb, void *data,
>  	if (!qp || !len)
>  		return -EINVAL;
>  
> -	/* If the qp link is down already, just ignore. */
>  	if (!qp->link_is_up)
> -		return 0;
> +		return -ENOLINK;
>  
>  	entry = ntb_list_rm(&qp->ntb_tx_free_q_lock, &qp->tx_free_q);
>  	if (!entry) {