Commit 87671375 authored May 11, 2019 by Vladimir Oltean Committed by David S. Miller May 12, 2019

net: dsa: Initialize DSA_SKB_CB(skb)->deferred_xmit variable



The sk_buff control block can have any contents on xmit put there by the
stack, so initialization is mandatory, since we are checking its value
after the actual DSA xmit (the tagger may have changed it).

The DSA_SKB_ZERO() macro could have been used for this purpose, but:
- Zeroizing a 48-byte memory region in the hotpath is best avoided.
- It would have triggered a warning with newer compilers since
  __dsa_skb_cb contains a structure within a structure, and the {0}
  initializer was incorrect for that purpose.

So simply remove the DSA_SKB_ZERO() macro and initialize the
deferred_xmit variable by hand (which should be done for all further
dsa_skb_cb variables which need initialization - currently none - to
avoid the performance penalty).

Fixes: 97a69a0d ("net: dsa: Add support for deferred xmit")
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 8f779443

include/net/dsa.h

+0 −3

Original line number	Diff line number	Diff line
		@@ -102,9 +102,6 @@ struct __dsa_skb_cb {
		#define DSA_SKB_CB_COPY(nskb, skb) \
		{ __DSA_SKB_CB(nskb) = __DSA_SKB_CB(skb); }

		#define DSA_SKB_CB_ZERO(skb) \
		{ *__DSA_SKB_CB(skb) = (struct __dsa_skb_cb) {0}; }

		#define DSA_SKB_CB_PRIV(skb) \
		((void *)(skb)->cb + offsetof(struct __dsa_skb_cb, priv))

net/dsa/slave.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -463,6 +463,8 @@ static netdev_tx_t dsa_slave_xmit(struct sk_buff skb, struct net_device dev)
		s->tx_bytes += skb->len;
		u64_stats_update_end(&s->syncp);

		DSA_SKB_CB(skb)->deferred_xmit = false;

		/* Identify PTP protocol packets, clone them, and pass them to the
		* switch driver
		*/

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