Re: open by handle support for NFS V2

["J. Bruce Fields" <bfields@fieldses.org>]

On Sat, Jul 01, 2017 at 11:34:36AM +0200, Mkrtchyan, Tigran wrote:
> 
> 
> ----- Original Message -----
> > From: "J. Bruce Fields" <bfields@fieldses.org>
> > To: "Trond Myklebust" <trondmy@primarydata.com>
> > Cc: "Christoph Hellwig" <hch@lst.de>, "Jeff Layton" <jlayton@poochiereds.net>, "linux-nfs" <linux-nfs@vger.kernel.org>,
> > "schumaker anna" <schumaker.anna@gmail.com>
> > Sent: Friday, June 30, 2017 7:38:18 PM
> > Subject: Re: open by handle support for NFS V2
> 
> > On Fri, Jun 30, 2017 at 05:00:59PM +0000, Trond Myklebust wrote:
> >> The main use case for open by filehandle was (and still should be) the
> >> promise of being able to do the sort of tricks you normally associate
> >> with object storage on a standard filesystem.
> >> 
> >> Imagine that you are trying to build an application for indexing and
> >> searching the data on your storage. You basically want to trawl through
> >> the filesystem on a regular basis and build up a database of key words
> >> and other metadata to tell you what is in the files. For that kind of
> >> application, the namespace is a real PITA to deal with, because files
> >> get renamed, moved and deleted all the time; so if you can store
> >> something that is independent of the namespace and that will give you
> >> access to the file contents, then why wouldn't you do so? Normally,
> >> applications like that use the inode number, but you can't open a file
> >> by inode number, and you have the same problems with inode number reuse
> >> that a NFS server has.
> >> 
> >> That's the sort of thing I'd think we want to allow through open by
> >> filehandle, and I see no reason why NFS should be excluded from that
> >> type of application.
> > 
> > Thanks, that makes sense.
> > 
> > We've had open_by_handle support for most filesystems since 2011, is
> > there evidence of anyone doing this?
> 
> 
> I am pretty sure that nfs-ganesha is using this in one the backend
> implementations.

Yes, but I was curious about the kind of application Trond describes.

--b.