fsck_ufs locked in snaplk

[Chris Dillon]

Quoting Dmitry Morozovsky <marck at rinet.ru>:

> On Mon, 24 Apr 2006, Kris Kennaway wrote:
>
> KK> Also you should add DEBUG_LOCKS and DEBUG_VFS_LOCKS on the off chance
> KK> they catch the problem.
>
> I got one thought about the source of these hangs/crashes: this   
> machine is the
> only one with actively used quotas. I'll test the more thoroughly   
> this evening.

I had problems with snapshots and hangs in 5.x.  For that, a daily  
reboot would keep the problems at bay.  I upgraded to 6.0 and the  
problems completely disappeared.  I kept 6.0-STABLE running for weeks.  
  Somewhere along the line, as 6.1 approached, similar problems  
re-appeared, but not exactly the same as what I had in 5.x.  Now  
instead of a complete system hang, individual processes will hang  
while attempting to access a certain filesystem.  I'm running  
6.1-PRERELEASE from April 2 and for some reason since this weekend it  
has happened more often, but I'm not sure why since I haven't made any  
system changes since April 2.

I also am using quotas heavily with this system, and snapshoting every  
filesystem once a day.  The filesystem which processes will hang on  
when attempting to access it happens to be the one with quotas enabled.

I'm going to update to the latest 6.1 code this evening and enable  
INVARIANTS, WITNESS, and the two DEBUG_LOCKS options to the kernel to  
see if it catches anything.