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DragonFly kernel List (threaded) for 2003-09
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Re: cache_lookup() work this week.

From: Jan Grant <Jan.Grant@xxxxxxxxxxxxx>
Date: Fri, 5 Sep 2003 15:28:55 +0100 (BST)

On Fri, 5 Sep 2003, Billy wrote:

> On Fri, Sep 05, 2003 at 11:34:31AM +0100, Jan Grant wrote:
> > There are advantages in having a DAG for directory trees. I'm still
> > trying to figure out what good permitting cycles does.
> There are a few times that I've wished I could make directory hardlinks.  In
> most of these instances a soft link was good enough, however not always.
> When managing jails I like to put services in their own /services/xxx
> subdir, as well as under their respective /jails/host/services/xxx.  I
> then I can blow away the jail, or do a destructive upgrade without
> having to worry about restoring the service related data other than
> making another link.  Soft links don't work because of chroot.

Yup, that's exactly what I meant by the advantages in having a directory
DAG (cheap'n'painless nullfs). However, your example doesn't appear to
contain any cycles.

If _cycles_ appear in the directory tree, then a cycle-capable ref
counter needs to be used; they exist, but they're a bit clunky. I
honestly can't think of a decent use case for permitting them.

jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/
Tel +44(0)117 9287088 Fax +44 (0)117 9287112 http://ioctl.org/jan/
Goedel would be proud - I'm both inconsistent _and_ incomplete.

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