which local FS supports concurrent direct IO write?

Hello,

I'm looking for a FS in Linux that supports concurrent direct IO write.
ext4 supports concurrent direct IO read if we mount it with dioread_nolock,
but doesn't support concurrent writes. XFS doesn't support concurrent
direct IO at all. It locks the inode exclusive if it's direct IO. I tried
btrfs, and it seems it doesn't support concurrent direct IO either though I
haven't looked into its code.
Is there a local FS that support concurrent direct IO write? It seems NFS
supports it (
http://kevinclosson.wordpress.com/2011/08/12/file-systems-for-a-database-choose-one-that-couples-direct-io-and-concurrent-io-whats-this-have-to-do-with-nfs-harken-back-5-2-years-to-find-out/),
but I'm looking for local FS.

Thanks,
Da
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