[dm-devel] [PATCH 2/6] scsi_dh : increment the refcounts while calling activate
Shyam Iyer
shyam_iyer at dell.com
Thu Jul 29 04:46:51 UTC 2010
On 07/28/2010 06:59 PM, Moger, Babu wrote:
> Hold the refcounts for device and scsi_dh_data while calling handler's activate. This will make sure that devices and scsi_dh_data are not removed while activate is still in progress. Make sure to call put_device and kref_put in the handler after activate is complete.
>
> Signed-off-by: Babu Moger<babu.moger at lsi.com>
> ---
> --- linux-2.6.35-rc5/drivers/scsi/device_handler/scsi_dh.c.orig 2010-07-23 05:40:11.000000000 -0500
> +++ linux-2.6.35-rc5/drivers/scsi/device_handler/scsi_dh.c 2010-07-23 05:48:53.000000000 -0500
> @@ -228,7 +228,8 @@ store_dh_state(struct device *dev, struc
> * Activate a device handler
> */
> if (scsi_dh->activate)
> - err = scsi_dh->activate(sdev, NULL, NULL);
> + err = scsi_dh_activate(sdev->request_queue,
> + NULL, NULL);
> else
> err = 0;
> }
> @@ -431,6 +432,8 @@ EXPORT_SYMBOL_GPL(scsi_unregister_device
> * do not hold the lock in the caller which may be needed in fn.
> * @data - data passed to the function fn upon completion.
> *
> + * NOTE - Remember to call put_device and kref_put in the handler after
> + * calling the callback function. Otherwise things could become messy.
> */
> int scsi_dh_activate(struct request_queue *q, activate_complete fn, void *data)
> {
> @@ -450,9 +453,12 @@ int scsi_dh_activate(struct request_queu
> if (err)
> return err;
>
> - if (scsi_dh->activate)
> + if (scsi_dh->activate) {
> + kref_get(&sdev->scsi_dh_data->kref);
> err = scsi_dh->activate(sdev, fn, data);
>
Why not kref_put here instead of in the device handler.. It is easier to
associate the ref counts..
Also, you are removing the put_device here and adding them to the device
handler which can be avoided ..
> - put_device(&sdev->sdev_gendev);
> + } else
> + put_device(&sdev->sdev_gendev);
> +
> return err;
> }
> EXPORT_SYMBOL_GPL(scsi_dh_activate);
>
>
>
>
> --
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>
-Shyam Iyer
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