linux-kernel - Re: [PATCH] vfs: new O

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Message-ID: <20090925123747.GA31228@gallifrey>
Date:	Fri, 25 Sep 2009 13:37:47 +0100
From:	"Dr. David Alan Gilbert" <linux@...blig.org>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	Andreas Gruenbacher <agruen@...e.de>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfs: new O_NODE open flag

* Miklos Szeredi (miklos@...redi.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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