Re: [PATCH -V18 04/13] vfs: Allow handle based open on symlinks

Aneesh Kumar K. V
2010-08-24T10:34:40Z

On Tue, 24 Aug 2010 17:21:55 +1000, Nick Piggin <npiggin@kernel.dk> wrote:
> On Sat, Aug 21, 2010 at 03:12:15PM +0530, Aneesh Kumar K. V wrote:
> > On Sat, 21 Aug 2010 18:30:24 +1000, Nick Piggin <npiggin@kernel.dk> wrote:
> > > Thanks, I had both of the same concerns as Christoph with API
> > > change and exposing symlink fds last time I looked at the patces,
> > > actually.
> > >
> > > But they can probably be worked around or avoided. I think the more
> > > important thing is whether it is worth supporting. This is
> > > all restricted to root (or CAP_DAC_READ_SEARCH) only, right, and
> > > what exact semantics they want. I would like to see more discussion
> > > of what this enables and some results.
> > >
> > > For the case of avoiding expensive network revalidations in path name
> > > lookup, do we even need to open symlinks? Could the security issues be
> > > avoided by always having handle attached to an open fd?
> > >
> >
> > For implementing a userspace file server that use handle for
> > representing files (like NFS) we would require to have the ability to do
> > different file system operations that can operate on symlink to work on
> > handle too.
>
> Right. Is this a really important goal, I'm wondering? Is it realistic
> (ie. to be able to remove the nfs server from the kernel)?
>

The feature is also needed to implement a 9p virtio pass through file
system in Qemu http://thread.gmane.org/gmane.comp.emulators.qemu/68992

-aneesh