openvswitch: Fix alignment of struct sw_flow_key.

sw_flow_key alignment was declared as " __aligned(__alignof__(long))".
However, this breaks on the m68k architecture where long is 32 bit in
size but 16 bit aligned by default. This aligns to the size of a long to
ensure that we can always do comparsions in full long-sized chunks. It
also adds an additional build check to catch any reduction in alignment.

CC: Andy Zhou <azhou@nicira.com>
Reported-by: NFengguang Wu <fengguang.wu@intel.com>
Reported-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NJesse Gross <jesse@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/openvswitch/flow.c

@@ -1981,6 +1981,7 @@ int ovs_flow_to_nlattrs(const struct sw_flow_key *swkey,
  * Returns zero if successful or a negative error code. */
 int ovs_flow_init(void)
 {
+	BUILD_BUG_ON(__alignof__(struct sw_flow_key) % __alignof__(long));
 	BUILD_BUG_ON(sizeof(struct sw_flow_key) % sizeof(long));
 
 	flow_cache = kmem_cache_create("sw_flow", sizeof(struct sw_flow), 0,

net/openvswitch/flow.h

@@ -125,7 +125,7 @@ struct sw_flow_key {
 			} nd;
 		} ipv6;
 	};
-} __aligned(__alignof__(long));
+} __aligned(BITS_PER_LONG/8); /* Ensure that we can do comparisons as longs. */
 
 struct sw_flow {
 	struct rcu_head rcu;