What is the purpose of this feature ?
With dh_state functionality, one could associate a handler to a new
device and then if one does "multipath", the hardware handler would be
associated with the multipath device. What are we achieving by this ?
The review comments below are on the assumption that this is a needed
feature.
---
Shouldn't we provide a detach also ?
On Wed, 2008-05-14 at 16:43 +0200, Hannes Reinecke wrote:
> multipath keeps a separate device table which may be
> more current than the built-in one.
> So we should allow to override the multipath settings
> by calling ->attach for each device.
>
> Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
> ---
> drivers/md/dm-mpath.c | 10 ++++++
> drivers/scsi/device_handler/scsi_dh.c | 52 ++++++++++++++++++++++++++++++--
> include/scsi/scsi_dh.h | 1 +
> 3 files changed, 59 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
> index e8f704a..b69cd87 100644
> --- a/drivers/md/dm-mpath.c
> +++ b/drivers/md/dm-mpath.c
> @@ -546,6 +546,7 @@ static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
> {
> int r;
> struct pgpath *p;
> + struct multipath *m = (struct multipath *) ti->private;
>
> /* we need at least a path arg */
> if (as->argc < 1) {
> @@ -564,6 +565,15 @@ static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
> goto bad;
> }
>
> + if (m->hw_handler_name) {
> + r = scsi_dh_attach(bdev_get_queue(p->path.dev->bdev),
> + m->hw_handler_name);
> + if (r < 0) {
> + dm_put_device(ti, p->path.dev);
> + goto bad;
> + }
> + }
> +
> r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
> if (r) {
> dm_put_device(ti, p->path.dev);
> diff --git a/drivers/scsi/device_handler/scsi_dh.c b/drivers/scsi/device_handler/scsi_dh.c
> index 2dbf84b..dfca3db 100644
> --- a/drivers/scsi/device_handler/scsi_dh.c
> +++ b/drivers/scsi/device_handler/scsi_dh.c
> @@ -113,8 +113,12 @@ int scsi_dh_handler_attach(struct scsi_device *sdev,
> {
> int err = -EBUSY;
>
> - if (sdev->scsi_dh_data)
> - return err;
> + if (sdev->scsi_dh_data) {
> + if (sdev->scsi_dh_data->scsi_dh != scsi_dh)
> + return err;
> + else
> + return 0;
> + }
This need to be moved to an earlier patch.
>
> err = scsi_dh->attach(sdev);
>
> @@ -163,8 +167,11 @@ static int scsi_dh_notifier(struct notifier_block *nb,
> goto out;
>
> if (action == BUS_NOTIFY_ADD_DEVICE) {
> - scsi_dh_handler_attach(sdev, devinfo->handler);
> - device_create_file(dev, &scsi_dh_state_attr);
> + int err;
> +
> + err = scsi_dh_handler_attach(sdev, devinfo->handler);
> + if (!err)
> + err = device_create_file(dev, &scsi_dh_state_attr);
This too.
> } else if (action == BUS_NOTIFY_DEL_DEVICE) {
> if (sdev->scsi_dh_data == NULL)
> goto out;
> @@ -345,6 +352,43 @@ int scsi_dh_handler_exist(const char *name)
> }
> EXPORT_SYMBOL_GPL(scsi_dh_handler_exist);
>
> +/*
> + * scsi_dh_handler_attach - Attach device handler
> + * @sdev - sdev the handler should be attached to
> + * @name - name of the handler to attach
> + */
> +int scsi_dh_attach(struct request_queue *q, const char *name)
> +{
This code seems to do incorrect things (run the case with sdev == NULL
or sdev->scsi_dh_data->scsi_dh != scsi_dh).
This function can be simplified to just call scsi_dh_handler_attach()
after getting scsi_dh and a get_device.
We can avoid calling scsi_dh->attach directly. instead call
scsi_dh_device_handler(), which would do all the necessary checking.
> + unsigned long flags;
> + struct scsi_device *sdev;
> + struct scsi_device_handler *scsi_dh;
> + int err = 0;
> +
> + scsi_dh = get_device_handler(name);
> + if (!scsi_dh)
> + return -EINVAL;
> +
> + spin_lock_irqsave(q->queue_lock, flags);
> + sdev = q->queuedata;
> + if (sdev && sdev->scsi_dh_data) {
> + if (sdev->scsi_dh_data->scsi_dh != scsi_dh) {
> + err = -EBUSY;
> + } else {
> + spin_unlock_irqrestore(q->queue_lock, flags);
> + return 0;
> + }
> + }
> + if (!err || !get_device(&sdev->sdev_gendev))
> + err = -ENODEV;
> + spin_unlock_irqrestore(q->queue_lock, flags);
> +
> + if (scsi_dh->attach)
> + err = scsi_dh->attach(sdev);
> + put_device(&sdev->sdev_gendev);
> + return err;
> +}
> +EXPORT_SYMBOL_GPL(scsi_dh_attach);
> +
> static struct notifier_block scsi_dh_nb = {
> .notifier_call = scsi_dh_notifier
> };
> diff --git a/include/scsi/scsi_dh.h b/include/scsi/scsi_dh.h
> index 5d05ac0..567bd38 100644
> --- a/include/scsi/scsi_dh.h
> +++ b/include/scsi/scsi_dh.h
> @@ -59,3 +59,4 @@ enum {
>
> extern int scsi_dh_activate(struct request_queue *);
> extern int scsi_dh_handler_exist(const char *);
> +extern int scsi_dh_attach(struct request_queue *, const char *);
--
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