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List:       linux-aio
Subject:    Re: [Storage_sig] Re: New release of Linux POSIX AIO
From:       Sébastien_Dugué <sebastien.dugue () bull ! net>
Date:       2005-04-01 7:01:38
Message-ID: 1112338898.1408.43.camel () frecb000686
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On Thu, 2005-03-31 at 19:16 +0200, Laurent Vivier wrote:
> Le jeudi 31 mars 2005 à 11:06 -0500, Benjamin LaHaise a écrit :
> > On Thu, Mar 31, 2005 at 05:23:59PM +0200, Laurent Vivier wrote:
> > > > aio_reqprio and aio_lio_opcode.  Given the nature of priorities and 
> > > > the number of opcodes, a short provides a more than ample range.
> > > 
> > > On this point, I totally agree with you... but it seems it's not point
> > > of view of POSIX people.
> > 
> > In that case, why not have the fields that can overlap do and fixup the 
> > remainder?  The resulting aiocb would look like:
> > 
> > 	struct aiocb {
> > 		... first 64 bytes match iocb ...
> > 		int aio_reqprio;
> > 		int aio_lio_opcode;
> > 		struct sigevent aio_sigevent;
> > 	};
> > 
> 
> I think it's a very good solution.

  I second Laurent in that, sounds good.

> 
> > > Put I think this needs two user-to-kernel copies, one for iocb and one
> > > for sigevent.
> > > It's why our libposix-aio doesn't pass sigevent to kernel but only three
> > > useful values inside iocb when we create iocb from aiocb.
> > 
> > Sounds like a perfect job for __get_user_nocheck -- only copy the data 
> > that is needed into the in-kernel structures after validating the pointer.
> 
> Thank you for the tip ;-)
> 
> Sébastien, do you agree with all of that ?

  I do, that's what I had in mind.

> 
> > 		-ben
> 
> Regards,
> Laurent

  Sébastien.

-- 
------------------------------------------------------

  Sébastien Dugué                BULL/FREC:B1-247
  phone: (+33) 476 29 77 70      Bullcom: 229-7770

  mailto:sebastien.dugue@bull.net

  Linux POSIX AIO: http://www.bullopensource.org/posix
  
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