[Lustre-devel] Queries regarding LDLM_ENQUEUE

[Nicolas Williams]

On Wed, Oct 20, 2010 at 12:46:56PM -0400, Paul Nowoczynski wrote:
> 
> > The name_to_handle() only needs to be called on a single node, and 
> > open_by_handle() is called on the other nodes. I agree that this 
> > doesn't avoid the full O(n) RPCs for the open itself  but at least it 
> > does avoid the full path traversal from every client and on the 
> > MDS (replacing it with an MPI broadcast of the handle).
> Andreas,
> excuse my ignorance, but why does open_by_handle() need to issue an 
> RPC?  If it's to obtain the layout, couldn't the layout be encoded into 
> the 'handle'?

If you don't mind having a huge handle, then yes, we could skip
additional RPCs.

A handle would have to consist of a {MGS address, FID, layout, access
type, capability}, or so.