From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 27 May 2001 16:44:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 27 May 2001 16:44:01 -0400 Received: from humbolt.nl.linux.org ([131.211.28.48]:28689 "EHLO humbolt.nl.linux.org") by vger.kernel.org with ESMTP id ; Sun, 27 May 2001 16:43:50 -0400 Content-Type: text/plain; charset=US-ASCII From: Daniel Phillips To: Edgar Toernig Subject: Re: Why side-effects on open(2) are evil. (was Re: [RFD w/info-PATCH]device arguments from lookup) Date: Sun, 27 May 2001 22:45:17 +0200 X-Mailer: KMail [version 1.2] Cc: Oliver Xymoron , linux-kernel , linux-fsdevel@vger.kernel.org In-Reply-To: <0105270036060Z.06233@starship> <3B1101ED.3BF181F6@gmx.de> In-Reply-To: <3B1101ED.3BF181F6@gmx.de> MIME-Version: 1.0 Message-Id: <01052722451714.06233@starship> Content-Transfer-Encoding: 7BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sunday 27 May 2001 15:32, Edgar Toernig wrote: > Daniel Phillips wrote: > > It won't, the open for "." is handled in the VFS, not the > > filesystem - it will open the directory. (Without needing to be > > told it's a directory via O_DIRECTORY.) If you do open("magicdev") > > you'll get the device, because that's handled by magicdevfs. > > You really mean that "magicdev" is a directory and: > > open("magicdev/.", O_RDONLY); > open("magicdev", O_RDONLY); > > would both succeed but open different objects? Yes, and: open("magicdev/.", O_RDONLY | O_DIRECTORY); open("magicdev", O_RDONLY | O_DIRECTORY); will both succeed and open the same object. > > I'm not claiming there isn't breakage somewhere, > > you break UNIX fundamentals. But I'm quite relieved now because I'm > pretty sure that something like that will never go into the kernel. OK, I'll take that as "I couldn't find a piece of code that breaks, so it's on to the legal issues". SUS doesn't seem to have a lot to say about this. The nearest thing to a ruling I found was "The special filename dot refers to the directory specified by its predecessor". Which is not the same thing as: open("foo", O_RDONLY) == open ("foo/.", O_RDONLY) I don't know about POSIX (I don't have it: a pox on standards organizations that don't make their standards freely available) but SUS doesn't seem to forbid this. -- Daniel