[Lustre-devel] How can the name_to_handle() syscall benefit Lustre

[Andreas Dilger]

On 2011-01-31, at 09:52, James Simmons wrote:
> Andreas Dilger wrote:
>> This is something that I think would be very useful for Lustre in conjunction with the Lustre MPI ADIO driver. The MPI rank-0 node
>> could do the path traversal and generate a file handle via name_to_handle() and then MPI broadcast the file handle to all of the
>> other MPI processes, which can use it to open the shared file. This could save many thousands of MDS RPCs to do path traversal for
>> each client in a large MPI job. 
> 
> I thought the name_to_handle syscall idea was shot down? 

I don't think it was shot down, as much as it hasn't yet been accepted.  I've tried to support it in a form that would be useful to Lustre/MPI, and while it isn't quite where I'd like it to be, I think the flaws in the implementation are not insurmountable.

The current proposal is lacking a well-defined permanent filesystem identifier in each handle (i.e. a UUID as part of the public fh structure), but I think Lustre can still include the UUID as part of the private fh and have the userspace code map that back to a specific Lustre mountpoint, since it would be implemented as part of the Lustre ADIO layer.

>> On 2011-01-29, at 12:16, Vilobh Meshram <vilobh.meshram at gmail.com> wrote:
>> How can the name_to_handle() syscall benefit Lustre ?
>> 
>> Any insights will be helpful.
>> 
>> Thanks,
>> Vilobh
>> Graduate Research Associate
>> Department of Computer Science
>> The Ohio State University Columbus Ohio
>> 
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>> 
>> 


Cheers, Andreas
--
Andreas Dilger 
Principal Engineer
Whamcloud, Inc.