linux-kernel - Re: [PATCH 5/5] block: genhd: add an interface to set disk's poll interval

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Message-ID: <1343069014.25735.28.camel@ejdallLaptop>
Date:	Mon, 23 Jul 2012 12:43:34 -0600
From:	Betty Dall <betty.dall@...com>
To:	Aaron Lu <aaron.lu@....com>
Cc:	Jeff Garzik <jgarzik@...ox.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Lin Ming <minggr@...il.com>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-ide@...r.kernel.org, Aaron Lu <aaron.lwe@...il.com>
Subject: Re: [PATCH 5/5] block: genhd: add an interface to set disk's poll
 interval

Hi Aaron,

On Mon, 2012-07-23 at 14:49 +0800, Aaron Lu wrote:
> Set the ODD's in kernel poll interval to 2s for the user in case the
> user is using an old distro on which udev will not set the system wide
> block parameter events_dfl_poll_msecs.
Why did you pick 2 seconds? 

> 
> Signed-off-by: Aaron Lu <aaron.lu@....com>
> ---
>  block/genhd.c         | 23 +++++++++++++++++------
>  drivers/scsi/sr.c     |  1 +
>  include/linux/genhd.h |  1 +
>  3 files changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index bdb3682..de9b9d9 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -1619,6 +1619,19 @@ static void disk_events_workfn(struct work_struct *work)
>  		kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
>  }
>  
> +int disk_events_set_poll_msecs(struct gendisk *disk, long intv)
> +{
> +	if (intv < 0 && intv != -1)
> +		return -EINVAL;
> +
> +	disk_block_events(disk);
> +	disk->ev->poll_msecs = intv;
> +	__disk_unblock_events(disk, true);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(disk_events_set_poll_msecs);
> +
>  /*
>   * A disk events enabled device has the following sysfs nodes under
>   * its /sys/block/X/ directory.
> @@ -1675,16 +1688,14 @@ static ssize_t disk_events_poll_msecs_store(struct device *dev,
>  {
>  	struct gendisk *disk = dev_to_disk(dev);
>  	long intv;
> +	int ret;
>  
>  	if (!count || !sscanf(buf, "%ld", &intv))
>  		return -EINVAL;
>  
> -	if (intv < 0 && intv != -1)
> -		return -EINVAL;
> -
> -	disk_block_events(disk);
> -	disk->ev->poll_msecs = intv;
> -	__disk_unblock_events(disk, true);
> +	ret = disk_events_set_poll_msecs(disk, intv);
> +	if (ret)
> +		return ret;
>  
>  	return count;
>  }
> diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
> index 2f159aa..78c4226 100644
> --- a/drivers/scsi/sr.c
> +++ b/drivers/scsi/sr.c
> @@ -869,6 +869,7 @@ static int sr_probe(struct device *dev)
>  	dev_set_drvdata(dev, cd);
>  	disk->flags |= GENHD_FL_REMOVABLE;
>  	add_disk(disk);
> +	disk_events_set_poll_msecs(disk, 2000);

Could you check that disk event's poll_msecs is the default (-1) before
setting it to 2s? I am thinking of a case when the probe happens after
the call to disk_events_poll_msecs_store() and this code would overwrite
the user specified value.

>  
>  	sdev_printk(KERN_DEBUG, sdev,
>  		    "Attached scsi CD-ROM %s\n", cd->cdi.name);
> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
> index 017a7fb..7414fb5 100644
> --- a/include/linux/genhd.h
> +++ b/include/linux/genhd.h
> @@ -418,6 +418,7 @@ extern void disk_block_events(struct gendisk *disk);
>  extern void disk_unblock_events(struct gendisk *disk);
>  extern void disk_flush_events(struct gendisk *disk, unsigned int mask);
>  extern unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask);
> +extern int disk_events_set_poll_msecs(struct gendisk *disk, long intv);
>  
>  /* drivers/char/random.c */
>  extern void add_disk_randomness(struct gendisk *disk);

-Betty

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