Re: [PATCH] vfs: new O_NODE open flag

Dr. David Alan Gilbert
2009-09-25T11:37:50Z

* Miklos Szeredi (miklos@szeredi.hu) wrote:
> On Fri, 25 Sep 2009, Andreas Gruenbacher wrote:
> > On Thursday, 24 September 2009 16:51:58 Miklos Szeredi wrote:
> > > This patch adds a new open flag, O_NODE. This flag means: open just
> > > the filesystem node instead of the object referenced by the node.
> >
> > What is the intended use for O_NODE?
>
> It lets userspace file descriptors reference a inode without actually
> "dereferencing" it to get the underlying object. This allows for a
> couple of new things:
>
> - opening a special file (device/socket/fifo) without side effects
>
> - opening a symlink
>
> - opening any type of file without any permission is also possible
> (of course the resuling file descriptor may not be read or written)
>
> The above allows fstat(), fchmod(), ioctl(), etc to be used for files
> previously not possible.

Given an fd opened in this way is it possible to reopen it normally and
be guarenteed to get the same object?

Dave
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