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

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Date:	Tue, 24 Jul 2012 07:52:14 +0800
From:	Aaron Lu <aaron.lu@....com>
To:	Betty Dall <betty.dall@...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

On Mon, Jul 23, 2012 at 12:43:34PM -0600, Betty Dall wrote:
> Hi Aaron,

Hi,

> 
> 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? 

Just a random pick, no special meaning here.
On newer distros, udev will also pick 2s for the events_dfl_poll_msecs
parameter, so I just followed that :-)
Do you see any problem with this setting?

> 
> > 
> > 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.

The block device sr0 is created by this driver in this probe function,
so the user should not be able to set the poll interval before probe,
right?

Thanks,
Aaron

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