A useful VFS change ...

Dustin Oprea myselfasunder at gmail.com
Thu Mar 13 21:11:56 MDT 2014

On Wed, Feb 26, 2014 at 1:30 PM, Jeremy Allison <jra at samba.org> wrote:

> On Wed, Feb 26, 2014 at 10:28:37AM -0800, Richard Sharpe wrote:
> > Hi folks,
> >
> > In discussions with Dustin an idea was proposed for a way to make VFS
> > writing easier for those who are accessing user-space file systems (of
> > which we are seeing more and more these days.)
> >
> > One of the problems is that a user-space file system cannot, in
> > general, fall through to vfs_defaults, because, except in limited
> > cases, these call into the kernel via syscalls with FDs that make no
> > sense to the kernel.
> >
> > This requires that the VFS write write code for every VFS function
> > with many of them simply returning ENOTSUP.
> >
> > By adding a set of flags to the structure we could simplify things.
> > Perhaps we should go back to the old idea of OPAQUE vs TRANSPARENT VFS
> > modules. The default is TRANSPARENT, but if the writer sets the OPAQUE
> > bit, the infrastructure will return ENOTSUP if a call is made to a VFS
> > function that is not implemented.
> Rather than complicating the structure, shouldn't we
> just create a new 'defaults' module that always returns
> ENOTSUP for every call, that OEMs can then stack their
> user-space filesystem modules on top of ?
> Jeremy.

It seems like this all just got dropped. Did we commit to make any changes
that might make a light transparent module not so painful to implement?


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