gmirror(8) and graid3(8) changes.

Hi.

Here you can find patches with changes to gmirror(8) and graid3(8):

	http://people.freebsd.org/~pjd/patches/gmirror.7.patch
	http://people.freebsd.org/~pjd/patches/graid3.patch

The patches does the following:
- Significant synchronization speed improvement. Now many parallel
  synchronization I/O requests can be used instead of only one before.
  Many people requested this.
- Close race between regular and synchronization requests (I wasn't able
  to trigger it with one sync request, but with many parallel requests
  it's real).
- Reimplement locking. I moved softc synchronization from the topology
  lock to per-device sx lock.

I'd like to ask gmirror/graid3 users to test those patches as much as
possible, because I want to commit them to the HEAD and RELENG_6
branches.

Because of locking changes it will be really good if you can turn on
INVARIANTS, INVARIANT_SUPPORT options and eventually DIAGNOSTIC in your
kernel.

Thanks in advance!

-- 
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd_at_FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!