freescale: Remove rcu_read_lock() around XDP program invocation

The dpaa and dpaa2 drivers have rcu_read_lock()/rcu_read_unlock() pairs
around XDP program invocations. However, the actual lifetime of the objects
referred by the XDP program invocation is longer, all the way through to
the call to xdp_do_flush(), making the scope of the rcu_read_lock() too
small. This turns out to be harmless because it all happens in a single
NAPI poll cycle (and thus under local_bh_disable()), but it makes the
rcu_read_lock() misleading.

Rather than extend the scope of the rcu_read_lock(), just get rid of it
entirely. With the addition of RCU annotations to the XDP_REDIRECT map
types that take bh execution into account, lockdep even understands this to
be safe, so there's really no reason to keep it around.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Camelia Groza <camelia.groza@nxp.com>
Cc: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Cc: Madalin Bucur <madalin.bucur@nxp.com>
Cc: Ioana Ciornei <ioana.ciornei@nxp.com>
Link: https://lore.kernel.org/bpf/20210624160609.292325-11-toke@redhat.com

diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
index 177c020..e682656 100644 (file)
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
@@ -2558,13 +2558,9 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr,
        u32 xdp_act;
        int err;
 
-       rcu_read_lock();
-
        xdp_prog = READ_ONCE(priv->xdp_prog);
-       if (!xdp_prog) {
-               rcu_read_unlock();
+       if (!xdp_prog)
                return XDP_PASS;
-       }
 
        xdp_init_buff(&xdp, DPAA_BP_RAW_SIZE - DPAA_TX_PRIV_DATA_SIZE,
                      &dpaa_fq->xdp_rxq);
@@ -2638,8 +2634,6 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void *vaddr,
                break;
        }
 
-       rcu_read_unlock();
-
        return xdp_act;
 }
 

diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
index 8433aa7..9733523 100644 (file)
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
@@ -352,8 +352,6 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv,
        u32 xdp_act = XDP_PASS;
        int err, offset;
 
-       rcu_read_lock();
-
        xdp_prog = READ_ONCE(ch->xdp.prog);
        if (!xdp_prog)
                goto out;
@@ -414,7 +412,6 @@ static u32 dpaa2_eth_run_xdp(struct dpaa2_eth_priv *priv,
 
        ch->xdp.res |= xdp_act;
 out:
-       rcu_read_unlock();
        return xdp_act;
 }