[PATCH 1/3] drm: Balance error path for GEM handle allocation

[Ville Syrjälä]

On Mon, Jan 04, 2016 at 10:18:50AM +0000, Chris Wilson wrote:
> On Mon, Jan 04, 2016 at 10:10:59AM +0000, Chris Wilson wrote:
> > The current error path for failure when establishing a handle for a GEM
> > object is unbalance, e.g. we call object_close() without calling first
> > object_open(). Use the typical onion structure to only undo what has
> > been set up prior to the error.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/drm_gem.c | 29 +++++++++++++++++------------
> >  1 file changed, 17 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> > index 2e10bba4468b..a08176debc0e 100644
> > --- a/drivers/gpu/drm/drm_gem.c
> > +++ b/drivers/gpu/drm/drm_gem.c
> > @@ -343,27 +343,32 @@ drm_gem_handle_create_tail(struct drm_file *file_priv,
> >  	spin_unlock(&file_priv->table_lock);
> >  	idr_preload_end();
> >  	mutex_unlock(&dev->object_name_lock);
> > -	if (ret < 0) {
> > -		drm_gem_object_handle_unreference_unlocked(obj);
> > -		return ret;
> > -	}
> > +	if (ret < 0)
> > +		goto err_unref;
> > +
> >  	*handlep = ret;
> >  
> >  	ret = drm_vma_node_allow(&obj->vma_node, file_priv->filp);
> > -	if (ret) {
> > -		drm_gem_handle_delete(file_priv, *handlep);
> > -		return ret;
> > -	}
> > +	if (ret)
> > +		goto err_remove;
> >  
> >  	if (dev->driver->gem_open_object) {
> >  		ret = dev->driver->gem_open_object(obj, file_priv);
> > -		if (ret) {
> > -			drm_gem_handle_delete(file_priv, *handlep);
> > -			return ret;
> > -		}
> > +		if (ret)
> > +			goto err_revoke;
> >  	}
> >  
> >  	return 0;
> > +
> > +err_revoke:
> > +	drm_vma_node_revoke(&obj->vma_node, file_priv->filp);
> > +err_remove:
> > +	spin_lock(&file_priv->table_lock);
> > +	idr_remove(&file_priv->object_idr, *handlep);
> 
> For bonus points, we could *handlep = 0; here.

For these sort of things I usually prefer to not clobber any
return parameters unless the whole operation suceeds.
 
> 
> > +	spin_unlock(&file_priv->table_lock);
> > +err_unref:
> > +	drm_gem_object_handle_unreference_unlocked(obj);
> > +	return ret;
> >  }
> 
> -- 
> Chris Wilson, Intel Open Source Technology Centre
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-- 
Ville Syrjälä
Intel OTC