Re: VFS: C99 sparse format for struct vfsops

On Mon, Jun 02, 2003 at 09:28:05AM -0700, Terry Lambert wrote:
> This is a different thing entirely... you are not adding
> elements in the cdevsw case.

	Er, huh?  Did you read Poul's HEADSUP mail for cdevsw sparse
	init?

> The VFSOP case is less of a problem than the VOP case, but it's
> still a problem.  Poul broke the VOP case a long time ago, when
> he added the default stuff, since there is no way to add a new
> default to an already existing array, and the entries with a
> default can't be proxied (e.g. over the network or to user space
> via a descriptor, per John Heidemann's original design for VFS
> stacking in UCLS's FICUS).

	OK, we are moving away from UCLS' FICUS.  Could you kindly
	provide me with some examples, and practicle use of this
	``adding'' a new default in an already existing array?

> By making this change, you are basically changing it from a
> data structure to something that has to be coded, and there's
> no way to add code for a new entry that needs to be defaulted
> to a non-NULL value --  which they all have to be.

	Huh? Come again please?  Could you ellaborate on this point as
	it is sending me in circles.  I don't see how it is not possible
	to do that, please provide a practical case, so I can
	understand.
	
> As I said above: Poul broke this for VOPs.  It doesn't make
> sense to say "It's broken for VOPs now, so it's OK to break it
> for VFSOPs, too".

	...

> It's "not been a problem", as you say, so far, because the VFS
> stacking in FreeBSD has been broken for a long time.  Breaking
> it more just moves us farther away from ever fixing the code,
> which I think is a bad thing.

	That is such of a broad statement..=

> If, at some point, we get rid of the "default" crap, then it
> would be possible to add VOPs to a running kernel by just
> reallocating the VOP array for each mounted FS to add the entry
> to the end of the array.

	And here is the question again, why would you want to add VOPs
	to a running kernel?  Please provide some examples, or practical
	cases.

> Your change makes this impossible for VFSOPS.

	Awaiting your reply...
	Cheers.
	
		-- Hiten (hmp_at_FreeBSD.ORG)