Subject: Re: Journaling for FFS
To: None <>
From: M J Fleming <>
List: tech-kern
Date: 10/02/2006 11:53:13
[Sorry about the empty reply]

On Sun, Oct 01, 2006 at 11:08:09PM -0700, Bill Studenmund wrote:
> That said, I think it's simpler to go with a physical-block journal. Get
> Dominic Giampaolo's book ("Practical File System Design with the Be File
> System") and it's well-discussed.

Thank you very much for this pointer, I found it's freely downloadble at

> You need two things for a journaling file system addition: 1) you need
> code to do the journal transactions. Giampaolo's book will give you that,
> at least as an overview. 2) You will need to look at all metadata writes
> and figure out how to journal them (you'll need this either way). i.e. how
> to inject transactions into the journal. Softdeps can be somewhat helpful
> here as it too will identify metadata update points, though it's only so
> helpful as you completely DON'T need the dependency stuff in softdeps,
> which may make it all confusing.

Despite the confusion of using softdeps to find when metadata needs updating
would be it better to use this in the long-run than some other solution? Or
perhaps (I'm only guessing I have little familiarity with the softdep code)
writing a generic mechanism which both the softdeps and other code could use?