Re: [PATCH v2 2/9] dmapool: cleanup error messages

[Matthew Wilcox <willy@infradead.org>]

On Fri, Aug 03, 2018 at 02:43:07PM -0400, Tony Battersby wrote:
> Out of curiosity, I just tried to create a dmapool with a NULL dev and
> it crashed on this:
> 
> static inline int dev_to_node(struct device *dev)
> {
> 	return dev->numa_node;
> }
> 
> struct dma_pool *dma_pool_create(const char *name, struct device *dev,
> 				 size_t size, size_t align, size_t boundary)
> {
> 	...
> 	retval = kmalloc_node(sizeof(*retval), GFP_KERNEL, dev_to_node(dev));
> 	...
> }
> 
> So either it needs more special cases for supporting a NULL dev, or the
> special cases can be removed since no one does that anyway.

Actually, it's worse.  dev_to_node() works with a NULL dev ... unless
CONFIG_NUMA is set.  So we're leaving a timebomb by pretending to
allow it.  Let's just 'if (!dev) return NULL;' early in create.