Re: Is there a reason we don't have kvfree_rcu()?

[George Spelvin <lkml@SDF.ORG>]

I'd just like to mention that the is_vmalloc_addr() test depends only on 
the virtual address, so can be done when the memory is queued, before the 
grace period.  That is, you could have kfree_rcu(), vfree_rcu(), and a 
kvfree_rcu() function which decides between them.

One advantage of that would be that you could put the vfree() sanity
checks into vfree_rcu(), so errors would have a useful backtrace,
and just do the __vunmap when the grace period expires.

Or you could build a mixed queue and do the is_vmalloc_addr() test at
the end of the grace period.  That was my original idea, because it
avoids the need for a separate queue.  (In the _rcu_bulk_data structure,
you can do a quicksort-style partitioning on is_vmalloc_addr(), so
the kfree_bulk() pointers are all contiguous.)

Just an implementation option.