[0/5] standardized waitqueue hashing

[William Lee Irwin III <wli@holomorphy.com>]

The following patch series consolidates the various instances of 
waitqueue hashing to use a uniform structure and share the per-zone
hashtable among all waitqueue hashers. This is expected to increase the
number of hashtable buckets available for waiting on bh's and inodes
and eliminate statically allocated kernel data structures for greater
node locality and reduced kernel image size. Some attempt was made to
look similar to Oleg Nesterov's suggested API in order to provide some
kind of credit for independent invention of something very similar (the
original versions of these patches predated my public postings on the
subject of filtered waitqueues).

These patches have the further benefit and intention of enabling aio
to use filtered wakeups by standardizing the data structure passed to
wake functions so that embedded waitqueue elements in aio structures
may be succesfully passed to the filtered wakeup wake functions, though
this patch series doesn't implement that particular functionality.

Successfully stress-tested on x86-64, and ia64 in recent prior versions.


-- wli