Cascaded VFS patch

[Andrew Bartlett]

Jean Francois Micouleau wrote:
> 
> On 17 Jun 2002, Simo Sorce wrote:
> 
> > I've just reviewed Alexander Cascaded VFS patch and found it ok,
> > now I'm attaching a new diff against current CVS to make it easy to test
> > before I commit it into the tree.
> > Unfortunately I have not much time to test it so I have a little request
> > for list attendees.
> 
> Just a note about the VFS I wanted to discuss with alexander at sambaXP
> but didn't have the time.
> 
> I don't like the idea that the vfs module see the vfs struct and muck with
> it at module's load time.
> 
> I would prefer something along all the vfs internal tables hidden to the
> vfs modules and only some vfs functions exported to the vfs modules.

I'm certainly a fan of hiding structs - there is a lot less damage these
things can do when they don't have access to 'the wrong things'.

> What I'm thinking is the samba vfs core exports 2 functions:
> vfs_register_module() and vfs_register_function(). On module loading (in
> the dl_open() function or whatever), the module calls this functions like
> that:
> 
> module_dlopen()
> {
>         vfs_register_module("my_vfs_module");
> 
>         vfs_register_function("my_vfs_module", "open", my_module_open);
>         vfs_register_function("my_vfs_module", "close", my_module_close);
>         vfs_register_function("my_vfs_module", "read", my_module_read);
>         vfs_register_function("my_vfs_module", "write", my_module_write);
> }
> 
> I thought of that while listening to the VFS presentation at sambaXP, I
> don't see why the vfs structs should be visible and more importantly it
> would allow modules to run even if samba vfs struct changes. Vfs modules
> maintainers wouldn't have to follow samba developement (and changes) as
> close as it's required now.

This sounds interesting, and would apply equally well for pdb and auth
modules.

It also works much better for the builtin-and-or-external case.

My only issue is with the complete loss of compile-time type checking.  

How should that be addressed?

Andrew Bartlett,

-- 
Andrew Bartlett                                 abartlet at pcug.org.au
Manager, Authentication Subsystems, Samba Team  abartlet at samba.org
Student Network Administrator, Hawker College   abartlet at hawkerc.net
http://samba.org     http://build.samba.org     http://hawkerc.net