Pawel Jakub Dawidek 40c7da090f Fix 3-way deadlock that can happen because of ZFS and vnode lock
order reversal.

thread0 (vfs_fhtovp)	thread1 (vop_getattr)	thread2 (zfs_recv)
--------------------	---------------------	------------------
			vn_lock
rrw_enter_read
						rrw_enter_write (hangs)
			rrw_enter_read (hangs)
vn_lock (hangs)

Submitted by:	Attila Nagy <bra@fsn.hu>
MFC after:	3 days
2010-04-15 16:40:54 +00:00
..