Re: [PATCH 10/14] scsi: osd: fix device_register() error handling

[James Bottomley <James.Bottomley@suse.de>]

On Sun, 2010-09-19 at 16:26 +0200, Dan Carpenter wrote:
> On Sun, Sep 19, 2010 at 04:55:07PM +0400, Vasiliy Kulikov wrote:
> > If device_register() fails then call put_device().
> > See comment to device_register.
> > 
> > Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
> > ---
> >  compile tested.
> > 
> >  drivers/scsi/osd/osd_uld.c |    4 +++-
> >  1 files changed, 3 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/scsi/osd/osd_uld.c b/drivers/scsi/osd/osd_uld.c
> > index cefb2c0..3e0edc2 100644
> > --- a/drivers/scsi/osd/osd_uld.c
> > +++ b/drivers/scsi/osd/osd_uld.c
> > @@ -474,7 +474,7 @@ static int osd_probe(struct device *dev)
> >  	error = device_register(&oud->class_dev);
> >  	if (error) {
> >  		OSD_ERR("device_register failed => %d\n", error);
> > -		goto err_put_cdev;
> > +		goto err_put_device;
> >  	}
> >  
> >  	get_device(&oud->class_dev);
> > @@ -482,6 +482,8 @@ static int osd_probe(struct device *dev)
> >  	OSD_INFO("osd_probe %s\n", disk->disk_name);
> >  	return 0;
> >  
> 
> Hm...  So if device_register() fails then we should always call
> device_put()?  It seems like a lot of existing code does that but I
> hadn't realized until now that that is how it works.

Heh, it wasn't a bug when most of the code was written.  It became a bug
when dev_set_name() was added because now the storage allocated for the
name has to be freed with a put.  Previous to this, the advice was just
to free the device if device_register() failed.

> Why can't the device_put() just be added inside the device_register() so
> the unwinding works automatically?

Since Greg and Kay didn't actually alter any of the device_register()
failure paths, this does sound to be the better course of action ... of
course, every device_register() introduced after the dev_set_name()
change may call put_device() on the cleanup path ... someone needs to
check.

James