Commit 751a587a authored Aug 21, 2015 by Jiri Benc Committed by David S. Miller Aug 23, 2015

route: fix breakage after moving lwtunnel state



__recnt and related fields need to be in its own cacheline for performance
reasons. Commit 61adedf3 ("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: 61adedf3 ("route: move lwtunnel state to dst_entry")
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 31fbde99

include/net/dst.h

+5 −2

Original line number	Diff line number	Diff line
		@@ -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;