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route: fix breakage after moving lwtunnel state

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__recnt and related fields need to be in its own cacheline for performance
reasons. Commit 61adedf3e3 ("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: 61adedf3e3 ("route: move lwtunnel state to dst_entry")
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jiri Benc 2015-08-21 12:41:14 +02:00 committed by David S. Miller
parent 31fbde9967
commit 751a587ac9
1 changed files with 5 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

7
include/net/dst.h
View file

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