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Date: Wed, 29 Nov 2000 09:52:01 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: Jens Axboe <axboe@suse.de>
cc: schwidefsky@de.ibm.com, linux-kernel@vger.kernel.org
Subject: Re: plug problem in linux-2.4.0-test11
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On Wed, 29 Nov 2000, Jens Axboe wrote:
> 
> I agree with your reasoning, even if the s390 behaviour is a bit
> "non-standard" wrt block devices. Linus, could you apply?
> 
> --- drivers/block/ll_rw_blk.c~	Wed Nov 29 15:17:33 2000
> +++ drivers/block/ll_rw_blk.c	Wed Nov 29 15:18:43 2000
> @@ -347,10 +347,9 @@
>   */
>  static inline void __generic_unplug_device(request_queue_t *q)
>  {
> -	if (!list_empty(&q->queue_head)) {
> -		q->plugged = 0;
> +	q->plugged = 0;
> +	if (!list_empty(&q->queue_head))
>  		q->request_fn(q);
> -	}
>  }

I would much rather actually go back to the original setup, which did
nothing at all if the queue wasn't plugged in the first place.

I think that we should strive for a setup that calls "request_fn" only to
start new IO, and that expects the low-level driver to be able to do the
whole request queue until it is empty. Then we re-start it the next time
around.

			Linus

-
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