Re: [RFC][WIP] DIO simplification and AIO-DIO stability

[Suparna Bhattacharya <suparna@in.ibm.com>]

On Thu, Feb 23, 2006 at 08:01:32PM -0500, Chris Mason wrote:
> On Thursday 23 February 2006 02:29, Suparna Bhattacharya wrote:
> > DIO code complexity and stability concerns were discussed way back during
> > OLS and Kernel summit last year. Still, the lack of a solid alternative and
> > motivation to subject oneself to the test of courage and delicate balance
> > that fiddling with this code entails, has meant that gingerly applying
> > fixes and bandaids as and when bugs are found, and moving on thereafter,
> > continues to be the most palatable option.
> >
> > A recent AIO-DIO bug reported by Kenneth Chen, came very close
> > to being the proverbial last straw for me. Hence, here is a rough attempt
> > to put together a (currently WIP) draft towards DIO code simplication,
> > based on suggestions that some of you have brought up at various times.
> > Several details, e.g. range locking implementation still need to be fleshed
> > out completely, ideas/comments/suggestions would be welcome.
> 
> I'm really in favor of this, and had actually started an implementation a 
> while back.  At the time, I posted a different version that added yet another 
> semaphore but simplified the rest of the locking (and held no locks during 
> the dio/aio).

Yes I have saved that patch as a reference as well.
With range locking I'm hoping that would be able to avoid the need for
i_hole_sem. Also I wanted to push out all locking code out of the DIO
code to avoid the various locking mode checks.

> 
> I'll try to dig up my original radix tagging code.  I'm not sure if I kept it, 
> but it did pass Daniel's dio vs buffer io racing tests at the time.

Cool - that would be great !

Regards
Suparna

> 
> -chris
> 
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-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India