Re: [PATCH/RFC 0/7] Volatile Filehandle Client-side Support

[Trond Myklebust <Trond.Myklebust@netapp.com>]

On Mon, 2011-11-14 at 08:07 +1100, NeilBrown wrote:

> If a server has objects that are never renamed, it can easily use volatile
> file handles.
> If a server has objects which can be renamed and wants to use volatile file
> handles, then if such an object is open and is about to be renamed, it must
> first log to stable storage some mapping to allow it to access the file from
> the old volatile file handle.  And of course it cannot allow renames during
> the grace period, but I think we already have that.
> Also, if the VFH is such that it will be  lost on a reboot, the server must
> log it to stable storage before allowing an open.

BTW: If the namespace is stable, then the server can easily implement
permanent filehandles. Use a hash of the pathname as the filehandle, and
set up a hidden directory ('/.filehandles') containing symlinks that map
said hash back to the correct pathname. No need for volatile
filehandles.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com