Multi-CPU harmless lockdep on x86 while copying data

[Christoph Hellwig]

On Tue, Mar 11, 2014 at 07:51:18AM +1100, Dave Chinner wrote:
> Yeah, b) seems like the way to simplify it - the filestreams code
> really only needs to track the parent/ag relationship rather than
> the child/parent relationship if there is a reliable way of
> determining the parent from the child.
> 
> What do we do with hardlinked files in this case? I'm happy to say
> "too bad" for these files mainly because the filestream allocator is
> aimed at associating multiple file creations together, so hard links
> really don't matter AFAICT...

We could flatly refuse filesystems for files with i_nlink > 1, or just
grab the first parent we get at.  Refusing seems like the better
alternative to me.