From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sat, 5 Dec 2015 15:03:54 +0800

Sorry Dave but you'll have to revert this because I've been able
to trigger the following crash with the patch:

Testing concurrent rhashtable access from 50 threads
------------[ cut here ]------------
kernel BUG at ../mm/vmalloc.c:1337!
invalid opcode: 0000 [#1] PREEMPT SMP 

The reason is that because I was testing insertions with BH disabled,
and __vmalloc doesn't like that, even with GFP_ATOMIC.  As we
obviously want to continue to support rhashtable users inserting
entries with BH disabled, we'll have to look for an alternate
solution.

Ok, reverted, thanks for the heads up.