__getcwd panics [lock held] (r193174, r193186)

Hi,

A recent change (r193174, r193186) in vfs_cache has been causing __getcwd to 
panic the system.  The panic appears to trigger when I try install lang/ezm3 
(with other things also happening).

-- hand copied ---

System call _getcwd returning with the following locks held:
shared rw Name Cache (Name Cache) r = 0 (0xc0eced7c) locked 
_at_ /usr/src/sys/kern/vfs_cache.c:1104
panic: witness_warn

--- above reproducible ---

cpuid = 2
KDB: enter: panic
[thread pid 23322 tid 100190 ]
Stopped at kdb_enter+0x3a: movl $0, kdb_why
db> cont
Uptime 20m35s
Physical memory: 3055 MB
Dumping 271 MB: 256 240 224panic: bufwrite: buffer is not busy???
cpuid = 0
KDB: enter: panic
[thread pid 25 tid 100055 ]
Stopped at kdb_enter+0x3a: movl $0, kdb_why
db> cont
Uptime: 20m36s
Automatic reboot in 15 seconds - press a key on the console to abort
Rebooting...
cpu_reset: Stopping other CPUs

--- systems hangs here, does nothing else ---
--- hard reset ---

I reverst the change (and r193175) and the panic 'disappeared'.  

Willing to test patches.  

Regards,

David