On Tue, 2008-05-20 at 16:05 +0200, Hannes Reinecke wrote:
> Implement a 'dh_state' sdev attribute for dynamic device handler
> manipulation. A read on the attribute will return the name of
> the currently attached device handler or 'detached' if no handler
> is attached.
> The attribute allows the following strings to be written:
> - The name of the device handler to be attached if the state is
> 'detached'.
> - 'activate' to trigger path activation if a device handler
> is attached.
> - 'detach' to detach the currently attached device handler.
>
> Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
> ---
> drivers/scsi/device_handler/scsi_dh.c | 107 ++++++++++++++++++++++++++++++++-
> 1 files changed, 105 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/device_handler/scsi_dh.c b/drivers/scsi/device_handler/scsi_dh.c
> index 0b5c457..b80fae7 100644
> --- a/drivers/scsi/device_handler/scsi_dh.c
> +++ b/drivers/scsi/device_handler/scsi_dh.c
> @@ -79,6 +79,98 @@ static void scsi_dh_handler_detach(struct scsi_device *sdev)
> }
>
> /*
> + * Functions for sysfs attribute 'dh_state'
> + */
> +static ssize_t
> +store_dh_state(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct scsi_device *sdev = to_scsi_device(dev);
> + struct scsi_device_handler *scsi_dh;
> + int err = -EINVAL;
> +
> + if (!sdev->scsi_dh_data) {
> + /*
> + * Attach to a device handler
> + */
> + if (!(scsi_dh = get_device_handler(buf)))
> + return err;
> + err = scsi_dh_handler_attach(sdev, scsi_dh);
> + } else {
> + if (!strncmp(buf, "detach", 6)) {
> + /*
> + * Detach from a device handler
> + */
> + scsi_dh_handler_detach(sdev);
> + err = 0;
> + } else if (!strncmp(buf, "activate", 8)) {
> + /*
> + * Activate a device handler
> + */
> + scsi_dh = sdev->scsi_dh_data->scsi_dh;
> + if (scsi_dh->activate)
> + err = scsi_dh->activate(sdev);
> + else
> + err = 0;
Sorry for the late comment. Why do we want to give the user to be able
to activate a path ? (I am assuming user as we do not want to be calling
this from multipath tools).
> + }
> + }
> +
> + return err<0?err:count;
> +}
> +
> +static ssize_t
> +show_dh_state(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> + struct scsi_device *sdev = to_scsi_device(dev);
> +
> + if (!sdev->scsi_dh_data)
> + return snprintf(buf, 20, "detached\n");
> +
> + return snprintf(buf, 20, "%s\n", sdev->scsi_dh_data->scsi_dh->name);
> +}
> +
> +static struct device_attribute scsi_dh_state_attr =
> + __ATTR(dh_state, S_IRUGO | S_IWUSR, show_dh_state,
> + store_dh_state);
> +
> +/*
> + * scsi_dh_sysfs_attr_add - Callback for scsi_init_dh
> + */
> +static int scsi_dh_sysfs_attr_add(struct device *dev, void *data)
> +{
> + struct scsi_device *sdev;
> + int err;
> +
> + if (!scsi_is_sdev_device(dev))
> + return 0;
> +
> + sdev = to_scsi_device(dev);
> +
> + err = device_create_file(&sdev->sdev_gendev,
> + &scsi_dh_state_attr);
> +
> + return 0;
> +}
> +
> +/*
> + * scsi_dh_sysfs_attr_remove - Callback for scsi_exit_dh
> + */
> +static int scsi_dh_sysfs_attr_remove(struct device *dev, void *data)
> +{
> + struct scsi_device *sdev;
> +
> + if (!scsi_is_sdev_device(dev))
> + return 0;
> +
> + sdev = to_scsi_device(dev);
> +
> + device_remove_file(&sdev->sdev_gendev,
> + &scsi_dh_state_attr);
> +
> + return 0;
> +}
> +
> +/*
> * scsi_dh_notifier - notifier chain callback
> */
> static int scsi_dh_notifier(struct notifier_block *nb,
> @@ -86,7 +178,7 @@ static int scsi_dh_notifier(struct notifier_block *nb,
> {
> struct device *dev = data;
> struct scsi_device *sdev;
> - int i, err = 0;
> + int i;
> struct scsi_device_handler *tmp, *devinfo = NULL;
>
> if (!scsi_is_sdev_device(dev))
> @@ -114,14 +206,19 @@ static int scsi_dh_notifier(struct notifier_block *nb,
> goto out;
>
> if (action == BUS_NOTIFY_ADD_DEVICE) {
> + int err;
> +
> err = scsi_dh_handler_attach(sdev, devinfo);
> + if (!err)
> + err = device_create_file(dev, &scsi_dh_state_attr);
we don't want to detach when we fail creating the file ? I am ok with
it, but just wanted to make sure that is what you intended.
> } else if (action == BUS_NOTIFY_DEL_DEVICE) {
> if (sdev->scsi_dh_data == NULL)
> goto out;
> + device_remove_file(dev, &scsi_dh_state_attr);
> scsi_dh_handler_detach(sdev);
> }
> out:
> - return err;
> + return 0;
why are we not returning err ?
> }
>
> /*
> @@ -275,11 +372,17 @@ static int __init scsi_dh_init(void)
>
> r = bus_register_notifier(&scsi_bus_type, &scsi_dh_nb);
>
> + if (!r)
> + bus_for_each_dev(&scsi_bus_type, NULL, NULL,
> + scsi_dh_sysfs_attr_add);
> +
> return r;
> }
>
> static void __exit scsi_dh_exit(void)
> {
> + bus_for_each_dev(&scsi_bus_type, NULL, NULL,
> + scsi_dh_sysfs_attr_remove);
> bus_unregister_notifier(&scsi_bus_type, &scsi_dh_nb);
> }
>
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