Re: [PATCH, RFC] simplify writeback thread creation

[Jens Axboe <axboe@kernel.dk>]

On 2010-07-09 09:52, Artem Bityutskiy wrote:
> On Thu, 2010-07-08 at 20:48 +0200, Christoph Hellwig wrote:
>> On Thu, Jul 08, 2010 at 09:43:22PM +0300, Artem Bityutskiy wrote:
>>> Hmm, was thinking about this while driving home - the forker approach
>>> has a good resilience property - if it cannot fork - it'll do the stuff
>>> itself. I have a feeling that if something like this to be implemented
>>> with the approach I suggested, we'll end up with similar level of
>>> complexity that we wanted to get rid of...
>>
>> Yes, the lazy starting is what adds the complexity.  I think starting
>> it once we have any filesystem mounted on the bdi and stop it once all
>> filesystems are gone is a lot simpler and more elegant.
> 
> But what about cases like 'dd if=/dev/zero of=/dev/sda4'? They also
> involve dirty data write-back.

You would have to do it at device open time, if the thread does
not already exist.

Not sure this is all worth it, I think the complexity of the
lazy create/exit is a bit exaggerated. 

-- 
Jens Axboe