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linux-next: build failure after merge of the net-next tree

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  linux-next: build failure after merge of the net-next tree Stephen Rothwell <sfr@canb.auug.org.au> - 2015-08-24 05:30 +0200
    Re: linux-next: build failure after merge of the net-next tree David Miller <davem@davemloft.net> - 2015-08-24 05:40 +0200
      Re: linux-next: build failure after merge of the net-next tree Stephen Rothwell <sfr@canb.auug.org.au> - 2015-08-24 06:30 +0200

#1211748 — linux-next: build failure after merge of the net-next tree

Hi all,

After merging the net-next tree, today's linux-next build (arm
multi_v7_defconfig) failed like this:

In function 'dst_hold',
    inlined from '__ipv6_dev_ac_dec' at /home/sfr/next/next/net/ipv6/anycast.c:328:2:
/home/sfr/next/next/include/linux/compiler.h:447:38: error: call to '__compiletime_assert_243' declared with attribute error: BUILD_BUG_ON failed: offsetof(struct dst_entry, __refcnt) & 63
  _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
                                      ^
/home/sfr/next/next/include/linux/compiler.h:430:4: note: in definition of macro '__compiletime_assert'
    prefix ## suffix();    \
    ^
/home/sfr/next/next/include/linux/compiler.h:447:2: note: in expansion of macro '_compiletime_assert'
  _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
  ^
/home/sfr/next/next/include/linux/bug.h:50:37: note: in expansion of macro 'compiletime_assert'
 #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
                                     ^
/home/sfr/next/next/include/linux/bug.h:74:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
  BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
  ^
/home/sfr/next/next/include/net/dst.h:243:2: note: in expansion of macro 'BUILD_BUG_ON'
  BUILD_BUG_ON(offsetof(struct dst_entry, __refcnt) & 63);
  ^

And many more :-(

Caused by commit

  61adedf3e3f1 ("route: move lwtunnel state to dst_entry")

I have used the net-next tree from next-20150821 for today.

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
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#1211751

From: Stephen Rothwell <sfr@canb.auug.org.au>
Date: Mon, 24 Aug 2015 13:21:11 +1000

> After merging the net-next tree, today's linux-next build (arm
> multi_v7_defconfig) failed like this:

Fixed by:

====================
[PATCH] 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>
---
 include/net/dst.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/net/dst.h b/include/net/dst.h
index 0a9a723..ef8f1d4 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;
-- 
2.1.0

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#1211772

Hi Dave,

On Sun, 23 Aug 2015 20:33:25 -0700 (PDT) David Miller <davem@davemloft.net> wrote:
>
> From: Stephen Rothwell <sfr@canb.auug.org.au>
> Date: Mon, 24 Aug 2015 13:21:11 +1000
> 
> > After merging the net-next tree, today's linux-next build (arm
> > multi_v7_defconfig) failed like this:
> 
> Fixed by:
> 
> ====================
> [PATCH] route: fix breakage after moving lwtunnel state

Thanks, I will get that tomorrow.  I must try to remember to check to
see if you have added fixes to your tree when I get these errors (not
that it happens all that often).

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
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