Re: [PATCH v4 2/5] scsi_dh: add scsi_dh_attached_handler_name

[Mike Snitzer <snitzer@redhat.com>]

Hi James,

Could you please stage this scsi_dh patch for the 3.5 merge?  The other
DM mpath patches in the patchset will go through Alasdair's DM tree.

Thanks,
Mike

On Thu, May 17 2012 at  6:58pm -0400,
Chandra Seetharaman <sekharan@us.ibm.com> wrote:

> Reviewed-by: Chandra Seetharaman <sekharan@us.ibm.com>
> 
> On Thu, 2012-05-10 at 17:31 -0400, Mike Snitzer wrote:
> > Introduce scsi_dh_attached_handler_name() to retrieve the name of the
> > scsi_dh that is attached to the scsi_device associated with the provided
> > request queue.  Returns NULL if a scsi_dh is not attached.
> > 
> > Also, fix scsi_dh_{attach,detach} function header comments to document
> > @q rather than @sdev.
> > 
> > Signed-off-by: Mike Snitzer <snitzer@redhat.com>
> > Tested-by: Babu Moger <babu.moger@netapp.com>
> > Cc: Hannes Reinecke <hare@suse.de>
> > Cc: Chandra Seetharaman <sekharan@us.ibm.com>
> > ---
> >  drivers/scsi/device_handler/scsi_dh.c |   38 ++++++++++++++++++++++++++++++++--
> >  include/scsi/scsi_dh.h                |    6 +++++
> >  2 files changed, 42 insertions(+), 2 deletions(-)
> > 
> > v4: fixed potential for returned string to be invalid (hch)
> > v3: fixed missing put_device that Babu pointed out
> > 
> > Index: linux-2.6/drivers/scsi/device_handler/scsi_dh.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/scsi/device_handler/scsi_dh.c
> > +++ linux-2.6/drivers/scsi/device_handler/scsi_dh.c
> > @@ -468,7 +468,8 @@ EXPORT_SYMBOL_GPL(scsi_dh_handler_exist)
> > 
> >  /*
> >   * scsi_dh_attach - Attach device handler
> > - * @sdev - sdev the handler should be attached to
> > + * @q - Request queue that is associated with the scsi_device
> > + *      the handler should be attached to
> >   * @name - name of the handler to attach
> >   */
> >  int scsi_dh_attach(struct request_queue *q, const char *name)
> > @@ -498,7 +499,8 @@ EXPORT_SYMBOL_GPL(scsi_dh_attach);
> > 
> >  /*
> >   * scsi_dh_detach - Detach device handler
> > - * @sdev - sdev the handler should be detached from
> > + * @q - Request queue that is associated with the scsi_device
> > + *      the handler should be detached from
> >   *
> >   * This function will detach the device handler only
> >   * if the sdev is not part of the internal list, ie
> > @@ -527,6 +529,38 @@ void scsi_dh_detach(struct request_queue
> >  }
> >  EXPORT_SYMBOL_GPL(scsi_dh_detach);
> > 
> > +/*
> > + * scsi_dh_attached_handler_name - Get attached device handler's name
> > + * @q - Request queue that is associated with the scsi_device
> > + *      that may have a device handler attached
> > + * @gfp - the GFP mask used in the kmalloc() call when allocating memory
> > + *
> > + * Returns name of attached handler, NULL if no handler is attached.
> > + * Caller must take care to free the returned string.
> > + */
> > +const char *scsi_dh_attached_handler_name(struct request_queue *q, gfp_t gfp)
> > +{
> > +	unsigned long flags;
> > +	struct scsi_device *sdev;
> > +	const char *handler_name = NULL;
> > +
> > +	spin_lock_irqsave(q->queue_lock, flags);
> > +	sdev = q->queuedata;
> > +	if (!sdev || !get_device(&sdev->sdev_gendev))
> > +		sdev = NULL;
> > +	spin_unlock_irqrestore(q->queue_lock, flags);
> > +
> > +	if (!sdev)
> > +		return NULL;
> > +
> > +	if (sdev->scsi_dh_data)
> > +		handler_name = kstrdup(sdev->scsi_dh_data->scsi_dh->name, gfp);
> > +
> > +	put_device(&sdev->sdev_gendev);
> > +	return handler_name;
> > +}
> > +EXPORT_SYMBOL_GPL(scsi_dh_attached_handler_name);
> > +
> >  static struct notifier_block scsi_dh_nb = {
> >  	.notifier_call = scsi_dh_notifier
> >  };
> > Index: linux-2.6/include/scsi/scsi_dh.h
> > ===================================================================
> > --- linux-2.6.orig/include/scsi/scsi_dh.h
> > +++ linux-2.6/include/scsi/scsi_dh.h
> > @@ -60,6 +60,7 @@ extern int scsi_dh_activate(struct reque
> >  extern int scsi_dh_handler_exist(const char *);
> >  extern int scsi_dh_attach(struct request_queue *, const char *);
> >  extern void scsi_dh_detach(struct request_queue *);
> > +extern const char *scsi_dh_attached_handler_name(struct request_queue *, gfp_t);
> >  extern int scsi_dh_set_params(struct request_queue *, const char *);
> >  #else
> >  static inline int scsi_dh_activate(struct request_queue *req,
> > @@ -80,6 +81,11 @@ static inline void scsi_dh_detach(struct
> >  {
> >  	return;
> >  }
> > +static inline const char *scsi_dh_attached_handler_name(struct request_queue *q,
> > +							gfp_t gfp)
> > +{
> > +	return NULL;
> > +}
> >  static inline int scsi_dh_set_params(struct request_queue *req, const char *params)
> >  {
> >  	return -SCSI_DH_NOSYS;
> > 
> 
>