On 07/01/17 11:34, Mkrtchyan, Tigran wrote:
----- Original Message -----
From: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
To: "Trond Myklebust" <trondmy@xxxxxxxxxxxxxxx>
Cc: "Christoph Hellwig" <hch@xxxxxx>, "Jeff Layton" <jlayton@xxxxxxxxxxxxxxx>, "linux-nfs" <linux-nfs@xxxxxxxxxxxxxxx>,
"schumaker anna" <schumaker.anna@xxxxxxxxx>
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.
Tigran is right: nfs-ganesha does something a bit similar to this in its
"FSAL_VFS" module (the backed module based the usage of on
open_by_handle_at() and name_to_handle_at() ).
regards
Philippe
--b.
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