[9fans] Quick question on fossil

[9fans] Quick question on fossil

[Roman V. Shaposhnik]

Hi!

I'm trying to read up on fossil implementation so
that I can sustain an intelligent conversation with
Andrey ;-)

Now, the paper "Fossil, an Archival File Server" is
pretty good, but here's one simple question that
I can't find an answer to: there's a pointer to
the root of the filesystem block from the Super.
But what is the data structure that is expected
to reside in that block? I thought it was VtRoot,
but looking at a hexdump of the fossil file -- it
doesn't look like one.

Thanks,
Roman.

Re: [9fans] Quick question on fossil

[Russ Cox]

On Mon, Jan 12, 2009 at 10:13 AM, Roman V. Shaposhnik <rvs@sun.com> wrote:
> I'm trying to read up on fossil implementation so
> that I can sustain an intelligent conversation with
> Andrey ;-)
>
> Now, the paper "Fossil, an Archival File Server" is
> pretty good, but here's one simple question that
> I can't find an answer to: there's a pointer to
> the root of the filesystem block from the Super.
> But what is the data structure that is expected
> to reside in that block? I thought it was VtRoot,
> but looking at a hexdump of the fossil file -- it
> doesn't look like one.

Super.active is the block number of a VtDirType block:
a block containing a few (I think 3) VtEntry structs.

VtRoot is the top of a vac archive.  it too contains
a pointer to a block containing a few VtEntry structs.
you could think of VtRoot as the vac equivalent of
fossil's Super.

if you

  cd /sys/src/cmd/fossil
  mk 8.view
  8.view /dev/sdC0/fossil

you should get a graphical file system data structure
browser, though since it is not part of the default
build it may not need some work to make
it build again.

russ

Re: [9fans] Quick question on fossil

[Roman V. Shaposhnik]

On Mon, 2009-01-12 at 11:06 -0800, Russ Cox wrote:
> Super.active is the block number of a VtDirType block:
> a block containing a few (I think 3) VtEntry structs.

Turns out there's one extra level of indirection there,
but your response was exactly what I needed to get
me unstuck. Thanks!

>   cd /sys/src/cmd/fossil
>   mk 8.view
>   8.view /dev/sdC0/fossil
>
> you should get a graphical file system data structure
> browser, though since it is not part of the default
> build it may not need some work to make
> it build again.

Wow! Thanks a bunch for mentioning that. It builds and
works flawlessly. What a treat!

Thanks,
Roman.