Re: [PATCH v1 3/5] IB/uverbs: ex_query_device: answer must depend on response buffer's size

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Hi,

Le jeudi 29 janvier 2015 à 11:38 -0700, Jason Gunthorpe a écrit :
> On Thu, Jan 29, 2015 at 07:00:00PM +0100, Yann Droneaud wrote:
> > As specified in "Extending Verbs API" presentation [1] by Tzahi Oved
> > during OFA International Developer Workshop 2013, the request's
> > comp_mask should describe the request data: it's describe the
> > availability of extended fields in the request.
> > Conversely, the response's comp_mask should describe the presence
> > of extended fields in the response.
> 
> This makes sense to me as well.
> 
> > -	err = ib_copy_to_udata(ucore, &resp, sizeof(resp));
> > +end:
> > +	err = ib_copy_to_udata(ucore, &resp, resp_len);
> >  	if (err)
> >  		return err;
> >  
> 
> I think resp_len should be returned, not 0?
> 

As said previously it's not possible to use the effective size of the
response as the return value of the write() syscall: the syscall
must return the size of the input buffer, not the size of the output
buffer, otherwise it would break the semantics of the write() syscall.

Regards.

-- 
Yann Droneaud
OPTEYA


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