Re: [PATCH] scsi: sd: unregister device if device_add_disk() failed in sd_probe()

[Luis Chamberlain]

On Fri, Dec 22, 2023 at 04:27:16PM +0800, Yu Kuai wrote:
> Hi,
> 
> 在 2023/12/22 14:49, Luis Chamberlain 写道:
> > On Fri, Dec 08, 2023 at 04:23:35PM +0800, linan666@xxxxxxxxxxxxxxx wrote:
> > > From: Li Nan <linan122@xxxxxxxxxx>
> > > 
> > > "if device_add() succeeds, you should call device_del() when you want to
> > > get rid of it."
> > > 
> > > In sd_probe(), device_add_disk() fails when device_add() has already
> > > succeeded, so change put_device() to device_unregister() to ensure device
> > > resources are released.
> > > 
> > > Fixes: 2a7a891f4c40 ("scsi: sd: Add error handling support for add_disk()")
> > > Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
> > 
> > Nacked-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> > 
> > > ---
> > >   drivers/scsi/sd.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> > > index 542a4bbb21bc..d81cbeee06eb 100644
> > > --- a/drivers/scsi/sd.c
> > > +++ b/drivers/scsi/sd.c
> > > @@ -3736,7 +3736,7 @@ static int sd_probe(struct device *dev)
> > >   	error = device_add_disk(dev, gd, NULL);
> > >   	if (error) {
> > > -		put_device(&sdkp->disk_dev);
> > > +		device_unregister(&sdkp->disk_dev);
> > >   		put_disk(gd);
> > >   		goto out;
> > >   	}
> > 
> > This is incorrect, device_unregister() calls:
> > 
> > void device_unregister(struct device *dev)
> > {
> > 	pr_debug("device: '%s': %s\n", dev_name(dev), __func__);
> > 	device_del(dev);
> > 	put_device(dev);
> > }
> > 
> > So you're adding what you believe to be a correct missing device_del().
> > But what you missed is that if device_add_disk() fails then device_add()
> > did not succeed because the new code we have in the kernel *today* unwinds
> > this for us now.
> 
> I'm confused here, there are two device here, one is 'sdkp->disk_dev',
> one is gendisk->part0->bd_device, and the order in which they
> initialize:
> 
> sd_probe
> device_add(&sdkp->disk_dev) -> succeed
> device_add_disk -> failed, and device_add(bd_device) did not succeed
> put_device(&sdkp->disk_dev) -> device_del is missed
> 
> I don't see that if device_add_disk() fail, device_del() for
> 'sdkp->disk_dev'is called from anywhere. Do I missing anything?

Ah then the fix is still incorrect and the commit log should
describe that this is for another device.

How about this instead?