From: Christoph Hellwig <hch@infradead.org>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
torvalds@linux-foundation.org, viro@ZenIV.linux.org.uk,
adilger@sun.com, dhowells@redhat.com, alan@lxorguk.ukuu.org.uk,
akpm@linux-foundation.org
Subject: Re: [RFC] O_NOACC: open without any access
Date: Tue, 23 Jun 2009 09:46:40 -0400 [thread overview]
Message-ID: <20090623134640.GA13831@infradead.org> (raw)
In-Reply-To: <E1MHBX7-0001Mv-Li@pomaz-ex.szeredi.hu>
On Thu, Jun 18, 2009 at 08:55:37AM +0200, Miklos Szeredi wrote:
> Implement a new open flag that doesn't require any access on the file.
> It works on any file type including symlinks.
>
> The sole purpose is to help race free "userspace lookup" type
> operations. So fstat, fch*, *at work but nothing else. Filesystem's
> ->open() is not called and f_op is set to NULL.
we guarantee that f_op is never NULL, so you'll need to assign a
file operations structure that is empty to it to avoid crashed in
various places.
> It would be logical to reuse the open_flag=3 value, but that has
> historically been used with different semantics so I'm afraid of
> touching it.
I think the historical semantics are exactly that you can open it
an issue ioctls + stat / etc on it ut not actually read/write it.
next prev parent reply other threads:[~2009-06-23 13:46 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-18 6:55 [RFC] O_NOACC: open without any access Miklos Szeredi
2009-06-23 13:46 ` Christoph Hellwig [this message]
2009-06-23 14:12 ` Miklos Szeredi
2009-06-23 14:34 ` Christoph Hellwig
2009-06-23 15:13 ` Miklos Szeredi
2009-06-23 15:52 ` David Howells
2009-06-23 16:06 ` Alan Cox
2009-06-23 16:10 ` David Howells
2009-06-23 16:31 ` Miklos Szeredi
2009-06-23 16:33 ` Alan Cox
2009-06-23 17:05 ` David Howells
2009-06-23 17:34 ` Linus Torvalds
2009-06-23 20:04 ` Miklos Szeredi
2009-06-24 10:53 ` Al Viro
2009-06-24 11:12 ` Miklos Szeredi
2009-06-24 16:40 ` Linus Torvalds
2009-06-23 22:44 ` David Howells
2009-06-23 17:20 ` David Howells
2009-06-23 16:53 ` Christoph Hellwig
2009-06-23 16:59 ` David Howells
2009-06-24 17:02 ` Ulrich Drepper
2009-06-24 18:06 ` Miklos Szeredi
2009-06-24 18:34 ` Ulrich Drepper
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