Re: [PATCH] [RFC] Add support for uevents on block device idle changes

[Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>]

On Tuesday 17 November 2009 15:37:39 Matthew Garrett wrote:

> @@ -1452,6 +1452,15 @@ static inline void __generic_make_request(struct bio *bio)
>  		if (should_fail_request(bio))
>  			goto end_io;
>  
> +		if (bio->bi_bdev->bd_disk->hysteresis_time &&
> +		    bio_has_data(bio) &&
> +		    !mod_timer(&bio->bi_bdev->bd_disk->hysteresis_timer,
> +			       jiffies+msecs_to_jiffies
> +			       (bio->bi_bdev->bd_disk->hysteresis_time))) {
> +			bio->bi_bdev->bd_disk->idle = 0;
> +			schedule_work(&bio->bi_bdev->bd_disk->idle_notify);
> +		}
> +

Wouldn't it be more reliable to hook into places where block requests are
issued/completed instead of queued?  This way you will not miss special
requests (some of them are quite common in practice and may take a relatively
long time to execute, i.e. FLUSH CACHE).

-- 
Bartlomiej Zolnierkiewicz