[Lustre-devel] Query to understand the Lustre request/reply message

[Vilobh Meshram]

Thanks a lot Alexey for the reply.The information will be really useful.

Since I am using 1.8.1.1 for my research project I will have to rely on the
old API.Since in the source tree prior to 2.0 we do not have a
mdt/mdt_handler.c and layout.c files will have to work with the low level
buffer management structures(ptlrpc_request,lustre_msg_v2,etc).Do you know a
place or a function which make use of the old API which I can use as a
reference to write the RPC for my task.

Thanks,
Vilobh
*Graduate Research Associate*
*Department of Computer Science*
*The Ohio State University Columbus Ohio*


On Wed, Oct 13, 2010 at 12:20 AM, Alexey Lyashkov <
alexey.lyashkov at clusterstor.com> wrote:

>
> On Oct 13, 2010, at 07:06, Vilobh Meshram wrote:
>
> Thanks Alexey for the reply.Thanks a lot.
>
> I will try out the steps mentioned by you and see if I can add a new RPC
> for the task which I am thinking of to implement in Lustre.
>
> The RPC of which I am thinking of will not return the lock to the
> caller.Yes that rpc will have special code to reconstruct in replay phase.
>
> In that case possible you need look to 'setattr' functions - it have
> own mdt_reconstruct_setattr reconstructor, but that is need support on
> client side.
> typically that say - you need have special field in message to copy data
> from server reply.
>
>
> Just a last question from which release of Lustre can we make use of the
> new API.
>
> Is their any documentation which lists the use of the new API.If yes can
> you please point me to that ?
>
> lustre 1.x have a old PtlRPC API, lustre 2.0 have a mix of new and old, but
> have a migrate to use new API.
>
>
> Thanks again.
>
> Thanks,
> Vilobh
> *Graduate Research Associate*
> ***Department of Computer Science*
> ***The Ohio State University Columbus Ohio*
>
> On Tue, Oct 12, 2010 at 11:46 PM, Alexey Lyashkov <
> alexey.lyashkov at clusterstor.com> wrote:
>
>> That is depend of rpc type - is that RPC want to be return lock to caller
>> or not, and is that rpc want to have special code to reconstruct in replay
>> phase.
>> in general you need look to mdt/mdt_handler.c. mdt_get_info is good
>> example of simple rpc processing - but it use new PtlRPC api.
>> that is API hide of low level request structures and provide api to access
>> to message buffer by identifier.
>> to use that API you need define structure of own message in
>> ptlrpc/layout.c, and own command in enum mds_cmd_t, adjust array with
>> commands and write own handler.
>>
>>
>> On Oct 13, 2010, at 01:17, Vilobh Meshram wrote:
>>
>> Thanks Alexey.It was helpful.
>>
>> I have one more question :-
>>
>> If we want to add a new RPC with a new opcode are there any guidlines to
>> be followed in the Lustre File System.
>>
>> Also ,
>> 1)How does the MDS process the ptlrpc_request i.e how does the MDS extract
>> the buffer information from the ptlrpc_message.
>> 2)For every new RPC is the message length which is to be sent on wire (
>> including the fixed header size + the buffer size) dependent on the number
>> of buffers in the lustre request message i.e the count field in the
>> ptlrpc_prep_req() or the size of the size[] array.
>>
>>
>> Thanks,
>> Vilobh
>> *Graduate Research Associate
>> Department of Computer Science
>> The Ohio State University Columbus Ohio*
>>
>>
>> On Tue, Oct 12, 2010 at 2:21 PM, Alexey Lyashkov <
>> alexey.lyashkov at clusterstor.com> wrote:
>>
>>> Hi Vilobh,
>>>
>>> ldlm_cli_cancel_req is good example to use old PtlRPC API.
>>> for first you need allocate request buffer via ptlrpc_prep_req
>>> next is - allocate reply buffer via ptlrpc_req_set_repsize
>>> next - call ptlrpc_queue_wait to send message and wait reply.
>>>
>>> osc_getattr_async good example for new PtlRPC API and async RPC
>>> processing.
>>>
>>> if that isn't help you - please show a yours code to find a error.
>>>
>>> On Oct 12, 2010, at 20:55, Vilobh Meshram wrote:
>>>
>>> I want to understand the message encoding and decoding logic in lustre.I
>>> am planning to send a request to the MDS and based on the reply from MDs
>>> want to populate the
>>>
>>>    struct lustre_msg *rq_repbuf; /* client only, buf may be bigger than
>>> msg */
>>>    struct lustre_msg *rq_repmsg;
>>>
>>> I am trying this for a simple "Hello" message but not seeing the expected
>>> output.Sometime I even see Kernel Crash.
>>> If you can please give me some insight on the way the Lustre File system
>>> encodes decodes the messages sent accross nodes it would be helpful.
>>>
>>> Thanks,
>>> Vilobh
>>> *Graduate Research Associate
>>> Department of Computer Science
>>> The Ohio State University Columbus Ohio*
>>> _______________________________________________
>>> Lustre-devel mailing list
>>> Lustre-devel at lists.lustre.org
>>> http://lists.lustre.org/mailman/listinfo/lustre-devel
>>>
>>>
>>>
>>
>>
>
>
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