ocelot: Dont allocate another multicast list, use __dev_mc_sync [Linux 5.2]

ocelot: Dont allocate another multicast list, use __dev_mc_sync [Linux 5.2]

This Linux kernel change "ocelot: Dont allocate another multicast list, use __dev_mc_sync" is included in the Linux 5.2 release. This change is authored by Claudiu Manoil <claudiu.manoil [at] nxp.com> on Tue May 21 19:52:55 2019 +0300. The commit for this change in Linux stable tree is 40a1578 (patch).

ocelot: Dont allocate another multicast list, use __dev_mc_sync

Doing kmalloc in atomic context is always an issue,
more so for a list that can grow significantly.
Turns out that the driver only uses the duplicated
list of multicast mac addresses to keep track of
what addresses to delete from h/w before committing
the new list from kernel to h/w back again via set_rx_mode,
every time this list gets updated by the kernel.
Given that the h/w knows how to add and delete mac addresses
based on the mac address value alone, __dev_mc_sync should be
the much better choice of kernel API for these operations
avoiding the considerable overhead of maintaining a duplicated
list in the driver.

Signed-off-by: Claudiu Manoil <[email protected]>
Tested-by: Alexandre Belloni <[email protected]>
Acked-by: Alexandre Belloni <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

There are 47 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/net/ethernet/mscc/ocelot.c | 43 +++++++-------------------------------
 drivers/net/ethernet/mscc/ocelot.h |  4 ----
 2 files changed, 8 insertions(+), 39 deletions(-)

diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c
index d715ef4..02ad11e 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -593,45 +593,25 @@ static int ocelot_port_xmit(struct sk_buff *skb, struct net_device *dev)
    return NETDEV_TX_OK;
 }

-static void ocelot_mact_mc_reset(struct ocelot_port *port)
+static int ocelot_mc_unsync(struct net_device *dev, const unsigned char *addr)
 {
-   struct ocelot *ocelot = port->ocelot;
-   struct netdev_hw_addr *ha, *n;
+   struct ocelot_port *port = netdev_priv(dev);

-   /* Free and forget all the MAC addresses stored in the port private mc
-    * list. These are mc addresses that were previously added by calling
-    * ocelot_mact_mc_add().
-    */
-   list_for_each_entry_safe(ha, n, &port->mc, list) {
-       ocelot_mact_forget(ocelot, ha->addr, port->pvid);
-       list_del(&ha->list);
-       kfree(ha);
-   }
+   return ocelot_mact_forget(port->ocelot, addr, port->pvid);
 }

-static int ocelot_mact_mc_add(struct ocelot_port *port,
-                 struct netdev_hw_addr *hw_addr)
+static int ocelot_mc_sync(struct net_device *dev, const unsigned char *addr)
 {
-   struct ocelot *ocelot = port->ocelot;
-   struct netdev_hw_addr *ha = kzalloc(sizeof(*ha), GFP_ATOMIC);
-
-   if (!ha)
-       return -ENOMEM;
-
-   memcpy(ha, hw_addr, sizeof(*ha));
-   list_add_tail(&ha->list, &port->mc);
-
-   ocelot_mact_learn(ocelot, PGID_CPU, ha->addr, port->pvid,
-             ENTRYTYPE_LOCKED);
+   struct ocelot_port *port = netdev_priv(dev);

-   return 0;
+   return ocelot_mact_learn(port->ocelot, PGID_CPU, addr, port->pvid,
+                ENTRYTYPE_LOCKED);
 }

 static void ocelot_set_rx_mode(struct net_device *dev)
 {
    struct ocelot_port *port = netdev_priv(dev);
    struct ocelot *ocelot = port->ocelot;
-   struct netdev_hw_addr *ha;
    int i;
    u32 val;

@@ -643,13 +623,7 @@ static void ocelot_set_rx_mode(struct net_device *dev)
    for (i = ocelot->num_phys_ports + 1; i < PGID_CPU; i++)
        ocelot_write_rix(ocelot, val, ANA_PGID_PGID, i);

-   /* Handle the device multicast addresses. First remove all the
-    * previously installed addresses and then add the latest ones to the
-    * mac table.
-    */
-   ocelot_mact_mc_reset(port);
-   netdev_for_each_mc_addr(ha, dev)
-       ocelot_mact_mc_add(port, ha);
+   __dev_mc_sync(dev, ocelot_mc_sync, ocelot_mc_unsync);
 }

 static int ocelot_port_get_phys_port_name(struct net_device *dev,
@@ -1657,7 +1631,6 @@ int ocelot_probe_port(struct ocelot *ocelot, u8 port,
    ocelot_port->regs = regs;
    ocelot_port->chip_port = port;
    ocelot_port->phy = phy;
-   INIT_LIST_HEAD(&ocelot_port->mc);
    ocelot->ports[port] = ocelot_port;

    dev->netdev_ops = &ocelot_port_netdev_ops;
diff --git a/drivers/net/ethernet/mscc/ocelot.h b/drivers/net/ethernet/mscc/ocelot.h
index ba3b338..541fe41 100644
--- a/drivers/net/ethernet/mscc/ocelot.h
+++ b/drivers/net/ethernet/mscc/ocelot.h
@@ -441,10 +441,6 @@ struct ocelot_port {
    struct phy_device *phy;
    void __iomem *regs;
    u8 chip_port;
-   /* Keep a track of the mc addresses added to the mac table, so that they
-    * can be removed when needed.
-    */
-   struct list_head mc;

    /* Ingress default VLAN (pvid) */
    u16 pvid;

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