From: Andreas Dilger Subject: Re: Extended file stat: Splitting file- and fs-specific info? Date: Wed, 9 May 2012 07:51:21 -0600 Message-ID: References: <20120509002420.GL5091@dastard> <20120419140558.17272.74360.stgit@warthog.procyon.org.uk> <16281.1336508382@redhat.com> <20170.1336555274@redhat.com> <20120509111958.GA11345@infradead.org> <4FAA5B24.1020306@itwm.fraunhofer.de> <20120509120544.GA17535@infradead.org> <4FAA6230.7040700@itwm.fraunhofer.de> Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Cc: Christoph Hellwig , David Howells , Dave Chinner , bfields@fieldses.org, smfrench@gmail.com, ben@decadent.org.uk, Trond.Myklebust@netapp.com, roland@hack.frob.com, jra@samba.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-ext4@vger.kernel.org, linux-api@vger.kernel.org, libc-alpha@sourceware.org To: Bernd Schubert Return-path: Received: from idcmail-mo2no.shaw.ca ([64.59.134.9]:41308 "EHLO idcmail-mo2no.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753791Ab2EINvX convert rfc822-to-8bit (ORCPT ); Wed, 9 May 2012 09:51:23 -0400 In-Reply-To: <4FAA6230.7040700@itwm.fraunhofer.de> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 2012-05-09, at 6:25 AM, Bernd Schubert wrote: > On 05/09/2012 02:05 PM, Christoph Hellwig wrote: >> On Wed, May 09, 2012 at 01:55:16PM +0200, Bernd Schubert wrote: >>> The basic idea of generation numbers is to check if an inode was >>> recycled, so only if the tuple of inode-number and generation-number >>> matches we still have the same file. Kernel nfs >> >> NFS does not and should not look at the inode generation. Except for a >> bit of legacy code for the old pre-Linux 2.4 filehandles it looks at the >> opaque file handle returned and only interpreted by the filesystem. Any >> userspace NFS server should do the same. > > Ok, I didn't look how kernel NFS does it for quite some time already... > User space NFS only can do it beginning with 2.6.39 - given that user space also needs to support older kernels and other OSs, which might not have open_by_handle, userspace unfortunately cannot entirely rely on that feature. But even fewer kernels have sys_statxat() in them (i.e. none), so you can rely on that even less than open_by_handle()... Cheers, Andreas