Re: [PATCH 3/7] oxenstored: refactor request processing

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 24/03/2016 22:22, Boris Ostrovsky wrote:
> On 03/17/2016 01:51 PM, Jonathan Davies wrote:
>> Encapsulate the request in a record that is passed from do_input to
>> process_packet and input_handle_error.
>>
>> This will be helpful when keeping track of the requests made as part
>> of a
>> transaction.
>>
>> Signed-off-by: Jonathan Davies <jonathan.davies@citrix.com>
>> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> Reviewed-by: Jon Ludlam <jonathan.ludlam@citrix.com>
>> Reviewed-by: Euan Harris <euan.harris@citrix.com>
>> ---
>>   tools/ocaml/xenstored/process.ml |   15 ++++++++++-----
>>   1 file changed, 10 insertions(+), 5 deletions(-)
>>
>> diff --git a/tools/ocaml/xenstored/process.ml
>> b/tools/ocaml/xenstored/process.ml
>> index 7a73669..c92bec7 100644
>> --- a/tools/ocaml/xenstored/process.ml
>> +++ b/tools/ocaml/xenstored/process.ml
>> @@ -344,11 +344,11 @@ let function_of_type ty =
>>       | Xenbus.Xb.Op.Invalid           -> reply_ack do_error
>>       | _                              -> reply_ack do_error
>>   -let input_handle_error ~cons ~doms ~fct ~ty ~con ~t ~rid ~data =
>> +let input_handle_error ~cons ~doms ~fct ~con ~t ~req =
>>       let reply_error e =
>>           Packet.Error e in
>>       try
>> -        fct con t doms cons data
>> +        fct con t doms cons req.Packet.data
>>       with
>>       | Define.Invalid_path          -> reply_error "EINVAL"
>>       | Define.Already_exist         -> reply_error "EEXIST"
>> @@ -370,7 +370,10 @@ let input_handle_error ~cons ~doms ~fct ~ty ~con
>> ~t ~rid ~data =
>>   (**
>>    * Nothrow guarantee.
>>    *)
>> -let process_packet ~store ~cons ~doms ~con ~tid ~rid ~ty ~data =
>> +let process_packet ~store ~cons ~doms ~con ~req =
>> +    let ty = req.Packet.ty in
>> +    let tid = req.Packet.tid in
>> +    let rid = req.Packet.rid in
>>       try
>>           let fct = function_of_type ty in
>>           let t =
>> @@ -379,7 +382,7 @@ let process_packet ~store ~cons ~doms ~con ~tid
>> ~rid ~ty ~data =
>>               else
>>                   Connection.get_transaction con tid
>>               in
>> -        let response = input_handle_error ~cons ~doms ~fct ~ty ~con
>> ~t ~rid ~data in
>> +        let response = input_handle_error ~cons ~doms ~fct ~con ~t
>> ~req in
>>             (* Put the response on the wire *)
>>           send_response ty con t rid response
>> @@ -412,11 +415,13 @@ let do_input store cons doms con =
>>       if newpacket then (
>>           let packet = Connection.pop_in con in
>>           let tid, rid, ty, data = Xenbus.Xb.Packet.unpack packet in
>> +        let req = {Packet.tid; Packet.rid; Packet.ty; Packet.data} in
>> +
>
> I think this change breaks the build with older ocaml versions:
>
> root@haswell> ocamlopt -v
> The OCaml native-code compiler, version 4.00.1
> Standard library directory: /usr/lib64/ocaml
> root@haswell> ocamlopt -g -ccopt "    " -dtypes -I
> /root/tmp/xen/tools/ocaml/xenstored/../libs/xb -I
> /root/tmp/xen/tools/ocaml/xenstored/../libs/mmap -I
> /root/tmp/xen/tools/ocaml/xenstored/../libs/xc -I
> /root/tmp/xen/tools/ocaml/xenstored/../libs/eventchn -cc gcc -w F
> -warn-error F -c -o process.cmx process.ml
> root@haswell>
>
>
> root@ovs104> ocamlopt -v
> The Objective Caml native-code compiler, version 3.11.2
> Standard library directory: /usr/lib64/ocaml
> root@ovs104> ocamlopt -g -ccopt "    " -dtypes -I
> /root/tmp/xen/tools/ocaml/xenstored/../libs/xb -I
> /root/tmp/xen/tools/ocaml/xenstored/../libs/mmap -I
> /root/tmp/xen/tools/ocaml/xenstored/../libs/xc -I
> /root/tmp/xen/tools/ocaml/xenstored/../libs/eventchn -cc gcc -w F
> -warn-error F -c -o process.cmx process.ml
> File "process.ml", line 487, characters 23-24:
> Error: Syntax error
> root@ovs104>
>
> I don't know much about ocaml (OK, I know *nothing* about ocaml) so I
> can't say what exactly might be wrong.

Could you perhaps try this instead?

let req = {tid = Packet.tid; rid = Packet.rid; ty = Packet.ty; data =
Packet.data} in

It is most likely that the older version of Ocaml can't infer the order
of fields.

~Andrew

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