On 18.11.20 12:53, Sebastian Andrzej Siewior wrote:
> The size of struct qllc is 2 byte. The memory for is allocated, initialized,
> used and deallocated a few lines later.
>
> It is more efficient to avoid the allocation/free dance and keeping the
> variable on stack. Especially since the compiler is smart enough to not
> allocate the memory on stack but assign the values directly.
>
> Rename `qllcptr' to `qllc' and use it on stack.
>
Can we please shrink this down to
qllcptr = (struct qllc *) skb_put(...);
qllcptr->foo = bar;
...
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
> drivers/s390/net/ctcm_mpc.c | 24 ++++++------------------
> 1 file changed, 6 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/s390/net/ctcm_mpc.c b/drivers/s390/net/ctcm_mpc.c
> index 04a51cc89e74c..4ff51af44d338 100644
> --- a/drivers/s390/net/ctcm_mpc.c
> +++ b/drivers/s390/net/ctcm_mpc.c
> @@ -2049,11 +2049,10 @@ static void mpc_action_rcvd_xid7(fsm_instance *fsm, int event, void *arg)
> */
> static int mpc_send_qllc_discontact(struct net_device *dev)
> {
> - __u32 new_len = 0;
> struct sk_buff *skb;
> - struct qllc *qllcptr;
> struct ctcm_priv *priv = dev->ml_priv;
> struct mpc_group *grp = priv->mpcg;
> + struct qllc qllc;
>
> CTCM_PR_DEBUG("%s: GROUP STATE: %s\n",
> __func__, mpcg_state_names[grp->saved_state]);
> @@ -2080,31 +2079,20 @@ static int mpc_send_qllc_discontact(struct net_device *dev)
> case MPCG_STATE_FLOWC:
> case MPCG_STATE_READY:
> grp->send_qllc_disc = 2;
> - new_len = sizeof(struct qllc);
> - qllcptr = kzalloc(new_len, gfp_type() | GFP_DMA);
> - if (qllcptr == NULL) {
> - CTCM_DBF_TEXT_(MPC_ERROR, CTC_DBF_ERROR,
> - "%s(%s): qllcptr allocation error",
> - CTCM_FUNTAIL, dev->name);
> - return -ENOMEM;
> - }
> -
> - qllcptr->qllc_address = 0xcc;
> - qllcptr->qllc_commands = 0x03;
> -
> - skb = __dev_alloc_skb(new_len, GFP_ATOMIC);
>
> + skb = __dev_alloc_skb(sizeof(struct qllc), GFP_ATOMIC);
> if (skb == NULL) {
> CTCM_DBF_TEXT_(MPC_ERROR, CTC_DBF_ERROR,
> "%s(%s): skb allocation error",
> CTCM_FUNTAIL, dev->name);
> priv->stats.rx_dropped++;
> - kfree(qllcptr);
> return -ENOMEM;
> }
>
> - skb_put_data(skb, qllcptr, new_len);
> - kfree(qllcptr);
> + qllc.qllc_address = 0xcc;
> + qllc.qllc_commands = 0x03;
> +
> + skb_put_data(skb, &qllc, sizeof(struct qllc));
>
> if (skb_headroom(skb) < 4) {
> CTCM_DBF_TEXT_(MPC_ERROR, CTC_DBF_ERROR,
>
