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

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Message-ID: <20090925183523.GA6065@gallifrey>
Date:	Fri, 25 Sep 2009 19:35:23 +0100
From:	"Dr. David Alan Gilbert" <linux@...blig.org>
To:	Valdis.Kletnieks@...edu
Cc:	Miklos Szeredi <miklos@...redi.hu>,
	Andreas Gruenbacher <agruen@...e.de>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfs: new O_NODE open flag

* Valdis.Kletnieks@...edu (Valdis.Kletnieks@...edu) wrote:
> On Fri, 25 Sep 2009 13:37:47 BST, "Dr. David Alan Gilbert" said:
> 
> > Given an fd opened in this way is it possible to reopen it normally and
> > be guarenteed to get the same object?
> 
> It's not possible even without this flag. Consider:
> 
>         fd1 = open("/tmp/foo",flags);
>         rc = rename("/tmp/foo","/tmp/bar");
>         fd2 = open("/tmp/foo",flags);
> 
> Or were you asking if *absent that sort of tomfoolery* if it would work?

I know it's not possible without this flag, my interest is whether
it would be possible WITH this flag to promote an fd opened with the
O_NODE to a normal fd, guaranteeing that it's still operating on the
same object.  The case I'm (vaguely) thinking of is open with O_NODE,
fstat it, come to the conslusion it's not a device and then proceed
to open it and read from it.

Dave


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