From owner-freebsd-arch Mon Mar 11 1:35:10 2002 Delivered-To: freebsd-arch@freebsd.org Received: from mailhub.fokus.gmd.de (mailhub.fokus.gmd.de [193.174.154.14]) by hub.freebsd.org (Postfix) with ESMTP id 5BEC337B400 for ; Mon, 11 Mar 2002 01:35:07 -0800 (PST) Received: from beagle (beagle [193.175.132.100]) by mailhub.fokus.gmd.de (8.11.6/8.11.6) with ESMTP id g2B9YuR10106; Mon, 11 Mar 2002 10:34:56 +0100 (MET) Date: Mon, 11 Mar 2002 10:34:55 +0100 (CET) From: Harti Brandt To: Garance A Drosihn Cc: Poul-Henning Kamp , Subject: Re: Increasing the size of dev_t and ino_t In-Reply-To: Message-ID: <20020311102511.M516-100000@beagle.fokus.gmd.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Sun, 10 Mar 2002, Garance A Drosihn wrote: GAD>First, my starting assumption on the significance of the st_dev GAD>value. My take on that value is that if two files have the same GAD>value for their device, then you could remove one of those files GAD>and hardlink the other file to the name of the removed file. GAD>Hardlinks can not cross device boundaries, but if these two files GAD>have the same value for st_dev then that hard link would not be GAD>crossing a device boundry. Or, another way to think of it is that GAD>if two files have the same device-number, and if they both have an GAD>st_nlink count of 1, then removing one of those files will result GAD>in more space being available for the expansion of the other file. GAD>(perhaps after a reboot, to eliminate the question of open file GAD>descriptors keeping that first file around even though you have GAD>unlinked it). I do not know if the appropriate standards would GAD>agree with me on these views, but they seem like a logical premise. GAD>Otherwise, a st_dev value would have no special meaning at all. There is an explicit requirement in POSIX: it requires a given st_ino/st_dev pair to uniqely identify a file. I take this to mean: if two files have the same st_ino/st_dev pair, they are the same file. If I mount the same volume in different places in the tree any file on that volume must have the same st_ino/st_dev pair in both mount points. As worded by POSIX the st_ino/st_dev pairs are not required to be persistant through reboots. It can, however, be hard to implement persistant file handles for NFS based on non-persistant st_info/st_dev pairs. harti -- harti brandt, http://www.fokus.gmd.de/research/cc/cats/employees/hartmut.brandt/private brandt@fokus.fhg.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message