Re: How to best overload the fileops ?

On Fri, 2013-08-23 at 13:06 -0700, Yuri wrote:
> On 08/23/2013 10:02, John Baldwin wrote:
> > There is something similar: see devfs_ops_f in sys/fs/devfs/devfs_vnops.c.
> 
> devfs_ops_f is a local static fileops object for devfs. I don't see how 
> is this similar to our situation. devfs doesn't overload any other file 
> system, they are a file system on their own.
> 

I think the point is that devfs_ops_f provides several devfs-specific
methods and then "inherits" the rest by referencing the standard
vn_whatever functions.  Since John recommended that you expose the
fo_whatever methods, I think he's suggesting you build your ops table by
providing your own close method and fill in the rest of the table with
the now-exposed kqueue ops methods.

It's not as neat and clean as "class epollops : public kqueueops {...}"
but it's probably not as bad as using clever macros to try to turn C
into a sort of C++Lite.

-- Ian

> >
> > I don't think we need a generic framework for this, just expose the
> > relevant fo_ methods for kqueue ops and use them in your epoll_ops.
> 
> In epoll case, fileops object as a whole should be exposed and used for 
> fp->f_ops, except fo_close which is overloaded.
> 
> So would you think struct fileops* kqueue_fileops(); be ok then?
> 
> Yuri
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