route: fix breakage after moving lwtunnel state

__recnt and related fields need to be in its own cacheline for performance
reasons. Commit 61adedf3e3f1 ("route: move lwtunnel state to dst_entry")
broke that on 32bit archs, causing BUILD_BUG_ON in dst_hold to be triggered.

This patch fixes the breakage by moving the lwtunnel state to the end of
dst_entry on 32bit archs. Unfortunately, this makes it share the cacheline
with __refcnt and may affect performance, thus further patches may be
needed.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Fixes: 61adedf3e3f1 ("route: move lwtunnel state to dst_entry")
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 2 deletions

diff --git a/include/net/dst.h b/include/net/dst.h
index 0a9a723f6c19..ef8f1d43a203 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -44,7 +44,6 @@ struct dst_entry {
 #else
         void                    *__pad1;
 #endif
-        struct lwtunnel_state   *lwtstate;
         int                     (*input)(struct sk_buff *);
         int                     (*output)(struct sock *sk, struct sk_buff *skb);
 
@@ -85,11 +84,12 @@ struct dst_entry {
         __u32                   __pad2;
 #endif
 
+#ifdef CONFIG_64BIT
+        struct lwtunnel_state   *lwtstate;
         /*
          * Align __refcnt to a 64 bytes alignment
          * (L1_CACHE_SIZE would be too much)
          */
-#ifdef CONFIG_64BIT
         long                    __pad_to_align_refcnt[1];
 #endif
         /*
@@ -99,6 +99,9 @@ struct dst_entry {
         atomic_t                __refcnt;       /* client references    */
         int                     __use;
         unsigned long           lastuse;
+#ifndef CONFIG_64BIT
+        struct lwtunnel_state   *lwtstate;
+#endif
         union {
                 struct dst_entry        *next;
                 struct rtable __rcu     *rt_next;