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Date: Wed, 11 Mar 2015 16:18:37 -0700 (PDT)
From: Don Lewis <truckman@FreeBSD.org>
Subject: Re: file system change notifications
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Cc: freebsd-hackers@FreeBSD.org, int0dster@gmail.com,
 oliver.pinter@hardenedbsd.org, shawn.webb@hardenedbsd.org
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On 11 Mar, Mateusz Guzik wrote:
> On Wed, Mar 11, 2015 at 11:11:14PM +0100, Oliver Pinter wrote:
>> Take a look at dazuko kernel module. Probably you should forward port
>> them, because they are obsoleted.
>> 
> 
> I checked the module out of curiosity. Their approach was to wrap various
> syscalls and work from there. This is used to be the common approach
> several years back it has a lot of shortcomings, complete lack of
> reliability being the biggest one.
> 
> As for better implementation: current namecache does not guarantee name
> resolution (even if name was entered) and not all names end up in the
> cache in the first place.
> 
> Lack of reliability comes from the fact that the cache does not pin
> vnodes in any way.

I seem to recall reading a long time ago that DragonFly pins directories
in the cache, or something like that.