Re: [PATCH v2] net: thunderx: rework mac addresses list to u64 array

Vadim Lomovtsev
2018-04-06T12:07:54Z

Hi Robin,

On Fri, Apr 06, 2018 at 12:48:40PM +0100, Robin Murphy wrote:
> On 06/04/18 12:14, Vadim Lomovtsev wrote:
> > From: Vadim Lomovtsev <Vadim.Lomovtsev@cavium.com>
> >
> > It is too expensive to pass u64 values via linked list, instead
> > allocate array for them by overall number of mac addresses from netdev.
> >
> > This eventually removes multiple kmalloc() calls, aviod memory
> > fragmentation and allow to put single null check on kmalloc
> > return value in order to prevent a potential null pointer dereference.
> >
> > Addresses-Coverity-ID: 1467429 ("Dereference null return value")
> > Fixes: 37c3347eb247 ("net: thunderx: add ndo_set_rx_mode callback implementation for VF")
> > Signed-off-by: Vadim Lomovtsev <Vadim.Lomovtsev@cavium.com>
> > ---
> > Changes from v1 to v2:
> > - C99 syntax: update xcast_addr_list struct field mc[0] -> mc[];
> >
> > ---
> > drivers/net/ethernet/cavium/thunder/nic.h | 7 +-----
> > drivers/net/ethernet/cavium/thunder/nicvf_main.c | 28 +++++++++---------------
> > 2 files changed, 11 insertions(+), 24 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/cavium/thunder/nic.h b/drivers/net/ethernet/cavium/thunder/nic.h
> > index 5fc46c5a4f36..448d1fafc827 100644
> > --- a/drivers/net/ethernet/cavium/thunder/nic.h
> > +++ b/drivers/net/ethernet/cavium/thunder/nic.h
> > @@ -265,14 +265,9 @@ struct nicvf_drv_stats {
> > struct cavium_ptp;
> > -struct xcast_addr {
> > - struct list_head list;
> > - u64 addr;
> > -};
> > -
> > struct xcast_addr_list {
> > - struct list_head list;
> > int count;
> > + u64 mc[];
> > };
> > struct nicvf_work {
> > diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_main.c b/drivers/net/ethernet/cavium/thunder/nicvf_main.c
> > index 1e9a31fef729..a26d8bc92e01 100644
> > --- a/drivers/net/ethernet/cavium/thunder/nicvf_main.c
> > +++ b/drivers/net/ethernet/cavium/thunder/nicvf_main.c
> > @@ -1929,7 +1929,7 @@ static void nicvf_set_rx_mode_task(struct work_struct *work_arg)
> > work.work);
> > struct nicvf *nic = container_of(vf_work, struct nicvf, rx_mode_work);
> > union nic_mbx mbx = {};
> > - struct xcast_addr *xaddr, *next;
> > + u8 idx = 0;
> > if (!vf_work)
> > return;
> > @@ -1956,16 +1956,10 @@ static void nicvf_set_rx_mode_task(struct work_struct *work_arg)
> > /* check if we have any specific MACs to be added to PF DMAC filter */
> > if (vf_work->mc) {
> > /* now go through kernel list of MACs and add them one by one */
> > - list_for_each_entry_safe(xaddr, next,
> > - &vf_work->mc->list, list) {
> > + for (idx = 0; idx < vf_work->mc->count; idx++) {
> > mbx.xcast.msg = NIC_MBOX_MSG_ADD_MCAST;
> > - mbx.xcast.data.mac = xaddr->addr;
> > + mbx.xcast.data.mac = vf_work->mc->mc[idx];
> > nicvf_send_msg_to_pf(nic, &mbx);
> > -
> > - /* after receiving ACK from PF release memory */
> > - list_del(&xaddr->list);
> > - kfree(xaddr);
> > - vf_work->mc->count--;
> > }
> > kfree(vf_work->mc);
> > }
> > @@ -1996,17 +1990,15 @@ static void nicvf_set_rx_mode(struct net_device *netdev)
> > mode |= BGX_XCAST_MCAST_FILTER;
> > /* here we need to copy mc addrs */
> > if (netdev_mc_count(netdev)) {
> > - struct xcast_addr *xaddr;
> > -
> > - mc_list = kmalloc(sizeof(*mc_list), GFP_ATOMIC);
> > - INIT_LIST_HEAD(&mc_list->list);
> > + mc_list = kmalloc(sizeof(*mc_list) +
> > + sizeof(u64) * netdev_mc_count(netdev),
>
> FWIW if you really wanted to disambiguate that it's a structure and not just
> an array being allocated, then it could be expressed without explicit
> arithmetic:
>
> size = offsetof(typeof(*mc_list), mc[netdev_mc_count(netdev)]);
>
> but that's probably just a matter of personal preference at this point.
>
> Robin.
>

Thanks for reviewing it and for hint. From style perspective, I believe,
I should get rid off direct types names also, and use your suggestion here.

I'll update patch to v3, test and re-post.
Thank you for your time.

WBR,
Vadim

> > + GFP_ATOMIC);
> > + if (unlikely(!mc_list))
> > + return;
> > + mc_list->count = 0;
> > netdev_hw_addr_list_for_each(ha, &netdev->mc) {
> > - xaddr = kmalloc(sizeof(*xaddr),
> > - GFP_ATOMIC);
> > - xaddr->addr =
> > + mc_list->mc[mc_list->count] =
> > ether_addr_to_u64(ha->addr);
> > - list_add_tail(&xaddr->list,
> > - &mc_list->list);
> > mc_list->count++;
> > }
> > }
> >