Re: Extended file stat: Splitting file- and fs-specific info?
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On 05/09/2012 03:51 PM, Andreas Dilger wrote:
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 nfsNFS 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()...
Well, I didn't say that :) In summary, an application needs to try to use the open-by-handle call and if that is not supported, it has to fall back to traditional stat and generation-number-ioctl. And as I said before, open-by-handle very likely removes the requirement for generation numbers in sys_statxat().
Cheers, Bernd -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html