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Date:      Mon, 29 Jul 2002 19:13:42 -0400 (EDT)
From:      Robert Watson <rwatson@freebsd.org>
To:        "David E. Cross" <crossd@cs.rpi.edu>
Cc:        fs@freebsd.org, guptar@cs.rpi.edu
Subject:   Re: UFS Journaling Project
Message-ID:  <Pine.NEB.3.96L.1020729190915.46084A-100000@fledge.watson.org>
In-Reply-To: <200207291714.g6THESc08188@jenolen.cs.rpi.edu>

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On Mon, 29 Jul 2002, David E. Cross wrote:

> As some of you know "we" (CS Dept lab) are working on a UFS journal. 
> We've made decent progress so far (given we've never worked on this part
> of the code so far), but we've hit a block.  We need to store state
> information in the kernel... current journal offset, journal vnode, etc. 
> It seems the logical place to put this is in struct ufsmount (since each
> mount will have different state), but whenever we put a "struct
> ufsjournal *uj;" in we get corruptined inode messages; we have rebuilt
> kernel from nothing.  It seems that there are 2 copies of struct
> ufsmount, or something is using raw offsets. 
> 
> Question: How do we modify struct ufsmount without causing corruption,
> or where should we store a pointer to our state information? 

That's fairly odd.  When I added extended attribute support to UFS, I
simply stuck the new structure (ufs_extattr_per_mount) in struct ufsmount
and never looked back.  I can't, offhand, imagine what you're running into
-- ufsmount should only ever be in-memory, and never on disk.

Not sure I really have any useful suggestions, other perhaps than to
experiment a bit and see what exactly triggers the problem.  Try adding
long[] arrays at various points in the structure, and see what size and
location cause the problem to kick in.

Very strange...

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Network Associates Laboratories



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