Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754506Ab0GFXgr (ORCPT ); Tue, 6 Jul 2010 19:36:47 -0400 Received: from cantor2.suse.de ([195.135.220.15]:57461 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751545Ab0GFXgq (ORCPT ); Tue, 6 Jul 2010 19:36:46 -0400 Date: Wed, 7 Jul 2010 09:36:29 +1000 From: Neil Brown To: Dave Chinner Cc: "Aneesh Kumar K. V" , "J. Bruce Fields" , hch@infradead.org, viro@zeniv.linux.org.uk, adilger@sun.com, corbet@lwn.net, serue@us.ibm.com, hooanon05@yahoo.co.jp, linux-fsdevel@vger.kernel.org, sfrench@us.ibm.com, philippe.deniel@CEA.FR, linux-kernel@vger.kernel.org Subject: Re: [PATCH -V14 0/11] Generic name to handle and open by handle syscalls Message-ID: <20100707093629.10c2feab@notabene.brown> In-Reply-To: <20100706232351.GD25018@dastard> References: <1276621981-2774-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <871vbn2mk9.fsf@linux.vnet.ibm.com> <20100702064108.64034561@notabene.brown> <87iq4y29a6.fsf@linux.vnet.ibm.com> <20100706161002.GD7387@fieldses.org> <87eifgfsez.fsf@linux.vnet.ibm.com> <20100706232351.GD25018@dastard> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1154 Lines: 34 On Wed, 7 Jul 2010 09:23:51 +1000 Dave Chinner wrote: > > I can add a new syscall that returns > > > > struct fs_uuid { > > u8 fs_uuid[16]; > > }; > > > > long sys_get_fs_uuid(int dfd, char *name, struct fs_uuid *fsid, int flag); > > libblkid already provides the UUID to userspace applications, doesn't it? Yes and no. libblkid provides the uuid of the thing that uses a block device. That doesn't directly map to "UUID of a filesystem". There are two types of filesystem that I can think of for which libblkid cannot give a uuid. - network filesystems (or virtual filesystems, or fuse ) - filesystems which share a block device, such as btrfs. btrfs can have 'subvols' - multiple "filesystems" within the one (set of) block device(s). libblkid cannot be asked about these different subvols. libblkid is useful, but not a real solution. NeilBrown -- 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/