Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161276AbXAHN0K (ORCPT ); Mon, 8 Jan 2007 08:26:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751531AbXAHN0K (ORCPT ); Mon, 8 Jan 2007 08:26:10 -0500 Received: from nikam-dmz.ms.mff.cuni.cz ([195.113.20.16]:58011 "EHLO nikam.ms.mff.cuni.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751533AbXAHN0J (ORCPT ); Mon, 8 Jan 2007 08:26:09 -0500 Date: Mon, 8 Jan 2007 14:26:07 +0100 From: Martin Mares To: Miklos Szeredi Cc: pavel@ucw.cz, mikulas@artax.karlin.mff.cuni.cz, matthew@wil.cx, bhalevy@panasas.com, arjan@infradead.org, jaharkes@cs.cmu.edu, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, nfsv4@ietf.org Subject: Re: Finding hardlinks Message-ID: References: <20070104225929.GC8243@elf.ucw.cz> <20070105131235.GB4662@ucw.cz> <20070108112916.GB25857@elf.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1582 Lines: 37 Hello! > You mean POSIX compliance is impossible? So what? It is possible to > implement an approximation that is _at least_ as good as samefile(). > One really dumb way is to set st_ino to the 'struct inode' pointer for > example. That will sure as hell fit into 64bits and will give a > unique (alas not stable) identifier for each file. Opening two files, > doing fstat() on them and comparing st_ino will give exactly the same > guarantees as samefile(). Good, ... except that it doesn't work. AFAIK, POSIX mandates inodes to be unique until umount, not until inode cache expires :-) IOW, if you have such implementation of st_ino, you can emulate samefile() with it, but you cannot have it without violating POSIX. > 4 billion files, each with more than one link is pretty far fetched. Not on terabyte scale disk arrays, which are getting quite common these days. > And anyway, filesystems can take steps to prevent collisions, as they > do currently for 32bit st_ino, without serious difficulties > apparently. They currently do that usually by not supporting more than 4G files in a single FS. Have a nice fortnight -- Martin `MJ' Mares http://mj.ucw.cz/ Faculty of Math and Physics, Charles University, Prague, Czech Rep., Earth "Oh no, not again!" -- The bowl of petunias - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/