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Re: Extended file stat: Splitting file- and fs-specific info?
- From: Andreas Dilger <adilger at dilger dot ca>
- To: Bernd Schubert <bernd dot schubert at itwm dot fraunhofer dot de>
- Cc: Christoph Hellwig <hch at infradead dot org>,David Howells <dhowells at redhat dot com>,Dave Chinner <david at fromorbit dot com>,bfields at fieldses dot org,smfrench at gmail dot com,ben at decadent dot org dot uk,Trond dot Myklebust at netapp dot com,roland at hack dot frob dot com,jra at samba dot org,linux-fsdevel at vger dot kernel dot org,linux-nfs at vger dot kernel dot org,linux-cifs at vger dot kernel dot org,samba-technical at lists dot samba dot org,linux-ext4 at vger dot kernel dot org,linux-api at vger dot kernel dot org,libc-alpha at sourceware dot org
- Date: Wed, 9 May 2012 07:51:21 -0600
- Subject: Re: Extended file stat: Splitting file- and fs-specific info?
- References: <20120509002420.GL5091@dastard> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <20120509111958.GA11345@infradead.org> <4FAA5B24.email@example.com> <20120509120544.GA17535@infradead.org> <4FAA6230.firstname.lastname@example.org>
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()...