Re: Filesystem AIO read-write patches

[Matthew Wilcox <willy@debian.org>]

On Thu, Apr 24, 2003 at 10:41:03AM +0530, Suparna Bhattacharya wrote:
> -void blk_congestion_wait(int rw, long timeout)
> +int blk_congestion_wait_wq(int rw, long timeout, wait_queue_t *wait)
>  {
> -	DEFINE_WAIT(wait);
>  	wait_queue_head_t *wqh = &congestion_wqh[rw];
> +	DEFINE_WAIT(local_wait);
> +
> +	if (!wait)
> +		wait = &local_wait;
>  
>  	blk_run_queues();
> -	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
> +	prepare_to_wait(wqh, wait, TASK_UNINTERRUPTIBLE);
> +	if (!is_sync_wait(wait)) 
> +		return -EIOCBRETRY;
> +
>  	io_schedule_timeout(timeout);
> -	finish_wait(wqh, &wait);
> +	finish_wait(wqh, wait);
> +	return 0;
> +}
> +
> +void blk_congestion_wait(int rw, long timeout)
> +{
> +	blk_congestion_wait_wq(rw, timeout, NULL);
>  }

I don't like this one.  DEFINE_WAIT allocates stuff on the stack.  
And aio seems to allocate a lot more on the stack than normal io does.
How about the following instead:

int blk_congestion_wait_wq(int rw, long timeout, wait_queue_t *wait)
{
 	wait_queue_head_t *wqh = &congestion_wqh[rw];

 	blk_run_queues();
	prepare_to_wait(wqh, wait, TASK_UNINTERRUPTIBLE);
	if (!is_sync_wait(wait)) 
		return -EIOCBRETRY;

	io_schedule_timeout(timeout);
	finish_wait(wqh, wait);
	return 0;
}

void blk_congestion_wait(int rw, long timeout)
{
	DEFINE_WAIT(wait);
	blk_congestion_wait_wq(rw, timeout, &wait);
}

-- 
"It's not Hollywood.  War is real, war is primarily not about defeat or
victory, it is about death.  I've seen thousands and thousands of dead bodies.
Do you think I want to have an academic debate on this subject?" -- Robert Fisk