datapath: 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: Fengguang Wu <fengguang.wu@intel.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Jesse Gross <jesse@nicira.com>

diff --git a/datapath/flow.c b/datapath/flow.c
index 7a697a4..34e4443 100644 (file)
--- a/datapath/flow.c
+++ b/datapath/flow.c
@@ -1995,6 +1995,7 @@ nla_put_failure:
  * 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,

diff --git a/datapath/flow.h b/datapath/flow.h
index eda74f3..03eae03 100644 (file)
--- a/datapath/flow.h
+++ b/datapath/flow.h
@@ -127,7 +127,7 @@ 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;