linux-kernel - Re: [PATCH v4 3/3] PCI: endpoint: pci_epf

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Date:   Wed, 28 Feb 2018 15:46:04 +0100 (CET)
From:   Rolf Evers-Fischer <embedded24@...rs-fischer.de>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
cc:     Rolf Evers-Fischer <embedded24@...rs-fischer.de>, kishon@...com,
        bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, andy.shevchenko@...il.com,
        Rolf Evers-Fischer <rolf.evers.fischer@...iv.com>
Subject: Re: [PATCH v4 3/3] PCI: endpoint: pci_epf_create: remove goto
 labels

Hi Kishon and Lorenzo,

On Wed, 28 Feb 2018, Lorenzo Pieralisi wrote:

> On Wed, Feb 28, 2018 at 02:07:19PM +0100, Rolf Evers-Fischer wrote:
> > From: Rolf Evers-Fischer <rolf.evers.fischer@...iv.com>
> > 
> > Removes the goto labels completely, handles the errors at the
> > respective call site and just returns instead of jumping around.
> > 
> > Signed-off-by: Rolf Evers-Fischer <rolf.evers.fischer@...iv.com>
> > ---
> >  drivers/pci/endpoint/pci-epf-core.c | 30 +++++++++---------------------
> >  1 file changed, 9 insertions(+), 21 deletions(-)
> > 
> > diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
> > index 1878a6776519..cf2c4f6590a0 100644
> > --- a/drivers/pci/endpoint/pci-epf-core.c
> > +++ b/drivers/pci/endpoint/pci-epf-core.c
> > @@ -203,16 +203,14 @@ struct pci_epf *pci_epf_create(const char *name)
> >  	int len;
> >  
> >  	epf = kzalloc(sizeof(*epf), GFP_KERNEL);
> > -	if (!epf) {
> > -		ret = -ENOMEM;
> > -		goto err_ret;
> > -	}
> > +	if (!epf)
> > +		return ERR_PTR(-ENOMEM);
> >  
> >  	len = strchrnul(name, '.') - name;
> >  	epf->name = kstrndup(name, len, GFP_KERNEL);
> >  	if (!epf->name) {
> > -		ret = -ENOMEM;
> > -		goto free_epf;
> > +		kfree(epf);
> > +		return ERR_PTR(-ENOMEM);
> >  	}
> >  
> >  	dev = &epf->dev;
> > @@ -221,24 +219,14 @@ struct pci_epf *pci_epf_create(const char *name)
> >  	dev->type = &pci_epf_type;
> >  
> >  	ret = dev_set_name(dev, "%s", name);
> > -	if (ret)
> > -		goto put_dev;
> > -
> > -	ret = device_add(dev);
> > -	if (ret)
> > -		goto put_dev;
> > -
> > -	return epf;
> > +	if (!ret) {
> > +		ret = device_add(dev);
> > +		if (!ret)
> > +			return epf;
> > +	}
> 
> This is ugly, sorry. I should have been more explicit, I prefer
> this construct:
> 
> ret = dev_set_name(dev, "%s", name);
> if (ret) {
> 	kfree(epf->name);
> 	kfree(epf);
> 	return ERR_PTR(ret);
> }
> 
> ret = device_add(dev);
> if (ret) {
> 	put_device(dev);
> 	return ERR_PTR(ret);
> }
> 
> return epf;
> 
> Please send a v5 and let's be done with it.
> 

Thank you for your feedback. I agree with you. Hiding the correct return 
value under two levels of 'if' is not the best idea.

I will send a v5 containing the proposal from Lorenzo. There is only one
difference: We must call 'put_device()' in both error cases, because
we have already initialized the device before. We had also jumped into
'put_dev:' in both situations before.

The modified code will then look like this:

 ret = dev_set_name(dev, "%s", name);
 if (ret) {
 	put_device(dev);
 	return ERR_PTR(ret);
 }

 ret = device_add(dev);
 if (ret) {
 	put_device(dev);
 	return ERR_PTR(ret);
 }

 return epf;

Best regards,
 Rolf

> > -put_dev:
> >  	put_device(dev);
> >  	return ERR_PTR(ret);
> > -
> > -free_epf:
> > -	kfree(epf);
> > -
> > -err_ret:
> > -	return ERR_PTR(ret);
> >  }
> >  EXPORT_SYMBOL_GPL(pci_epf_create);
> >  
> > -- 
> > 2.16.2
> > 
>