Subject: Re: Don't use UFS_DIRHASH
To: Reinoud Zandijk <>
From: Rui Paulo <>
List: tech-kern
Date: 08/19/2006 21:00:50
On Aug 19, 2006, at 6:44 PM, Reinoud Zandijk wrote:

> On Sat, Jul 15, 2006 at 10:36:09AM +0100, David Malone wrote:
>> On Wed, Jul 12, 2006 at 12:31:22PM -0400, Thor Lancelot Simon wrote:
>>> Removing UFS_DIRHASH from our kernel configuration made the  
>>> problem go
>>> away.  Though it is possible that there is an underlying problem  
>>> of some
>>> kind in one of the allocators that is simply particularly badly  
>>> exposed
>>> by UFS_DIRHASH, it seems more likely that there is a problem  
>>> (which we
>>> haven't found yet) in UFS_DIRHASH itself.  The code has a history of
>>> similar problems on FreeBSD which seem to have ended only when  
>>> the entire
>>> kernel synchronization scheme in FreeBSD was reworked in FreeBSD 5.
>> FWIW, in FreeBSD I think we've tracked down all outstanding memory
>> corruption bugs in which DIRHASH was implicated and they all turned
>> out to be problems in other subsystems that used memory allocations
>> of the same size. It works fine both in FreeBSD 4, where we have
>> spl style synchronisation and in 5+, where the synchronisation is
>> mutex based. It is quite possible that we've missed something, but
>> we're not seeing any evidence of it in FreeBSD right now.
>> The most recent one that we've plugged was one related to IPv6  
>> neighbour
>> discovery:
> Has anyone looked at this in NetBSD? or is it from a different code  
> base?

NetBSD doesn't have the problem.