build failure with mason/for-linus tree

[Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>]

Hi Chris,

FYI, today I failed to build mason/for-linus tree as follows.

===============================================================================
...
/home/sat/src/linux-2.6/fs/btrfs/transaction.c: In function 'record_root_in_trans':
/home/sat/src/linux-2.6/fs/btrfs/transaction.c:293:3: error: implicit declaration of function 'smp_mb__before_atomic' [-Werror=implicit-function-declaration]
   smp_mb__before_atomic();
   ^
/home/sat/src/linux-2.6/fs/btrfs/transaction.c: In function 'commit_fs_roots':
/home/sat/src/linux-2.6/fs/btrfs/transaction.c:1065:4: error: implicit declaration of function 'smp_mb__after_atomic' [-Werror=implicit-function-declaration]
    smp_mb__after_atomic();
    ^
cc1: some warnings being treated as errors
...
===============================================================================

It can be solved by cherry-picking febdbfe.

===
commit febdbfe8a91ce0d11939d4940b592eb0dba8d663
Author: Peter Zijlstra <peterz@infradead.org>
Date:   Thu Feb 6 18:16:07 2014 +0100

    arch: Prepare for smp_mb__{before,after}_atomic()
    
    Since the smp_mb__{before,after}*() ops are fundamentally dependent on
    how an arch can implement atomics it doesn't make sense to have 3
    variants of them. They must all be the same.
===

Thanks,
Satoru