Re: open by handle support for NFS V2

From: "Mkrtchyan, Tigran" <tigran.mkrtchyan@desy.de>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Trond Myklebust <trondmy@primarydata.com>,
	Christoph Hellwig <hch@lst.de>,
	Jeff Layton <jlayton@poochiereds.net>,
	linux-nfs <linux-nfs@vger.kernel.org>,
	schumaker anna <schumaker.anna@gmail.com>
Subject: Re: open by handle support for NFS V2
Date: Sat, 1 Jul 2017 11:34:36 +0200 (CEST)	[thread overview]
Message-ID: <995885135.19496849.1498901676399.JavaMail.zimbra@desy.de> (raw)
In-Reply-To: <20170630173818.GC14868@fieldses.org>

----- 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.

Tigran.

> 
> --b.
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