From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH] UBIFS: fill f_fsid Date: Tue, 2 Sep 2008 17:02:20 -0400 Message-ID: <20080902210219.GA9856@infradead.org> References: <1220194366-12731-1-git-send-email-dedekind@infradead.org> <1220194366-12731-13-git-send-email-dedekind@infradead.org> <1220262187.2982.58.camel@pmac.infradead.org> <20080901150147.GA20323@infradead.org> <1220339032.4036.31.camel@sauron> <20080902170954.GE3086@webber.adilger.int> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Artem Bityutskiy , Christoph Hellwig , David Woodhouse , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Adrian Hunter To: Andreas Dilger Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:50653 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751364AbYIBVCW (ORCPT ); Tue, 2 Sep 2008 17:02:22 -0400 Content-Disposition: inline In-Reply-To: <20080902170954.GE3086@webber.adilger.int> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Sep 02, 2008 at 11:09:54AM -0600, Andreas Dilger wrote: > The fsid is supposed to be a persistent, unique identifier for the > filesystem, used by NFS in file handles. Using st_dev is unsafe, > because that may change from one server boot to the next, because > of device probing order, driver changes, etc. Also, not all filesystems > HAVE a valid st_dev in the first place, which is the whole reason > for this thread. > > I think a ->get_fsid() export method would be preferable. Umm, different things. f_fsid in stat(v)fs is just a cookie exported to userspac that has never really been documented. We also called the filesystem part of the NFS filehandle in a few places, and for those it's correct that it should be stable. Currently the fsid is either created from the dev_t in kernelspace or from uuids extracted through libuuid in userspace. I can't see anything in the message that started this thread that mentions NFS, btw.