Hi Aaron,

On Tue, 2012-07-24 at 07:52 +0800, Aaron Lu wrote:

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

quoted

Hi Aaron,

Hi,

quoted

On Mon, 2012-07-23 at 14:49 +0800, Aaron Lu wrote:

quoted

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?

No problem, and I was curious as to why 2s, and the fact that is it used
in udev for events_dfl_poll_msecs is a good reason.

quoted

quoted

Signed-off-by: Aaron Lu <redacted>
---
 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?

The add_disk() call happens immediately before the new
disk_events_set_poll_msecs() call. add_disk() is what eventually creates
the sysfs files and calls your new disk_events_set_poll_msecs(). It
makes more sense to me to have the new call to
disk_events_set_poll_msecs(disk, 2000) before the call to add_disk().
That way add_disk()could override the 2 second default based on user
input. If a distro doesn't support udev setting events_dfl_poll_msecs,
the add_disk() won't ever make a call to disk_events_set_poll_msecs()
and the 2 second default will stand.

-Betty