On Mon, Sep 20, 2021 at 09:27:25AM +0200, Christoph Hellwig wrote: ... > diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c > index ef4950f808326..bbeb3f46db157 100644 > --- a/drivers/nvdimm/pmem.c > +++ b/drivers/nvdimm/pmem.c > @@ -328,6 +328,49 @@ static const struct dax_operations pmem_dax_ops = { > .zero_page_range = pmem_dax_zero_page_range, > }; > > +static ssize_t write_cache_show(struct device *dev, > + struct device_attribute *attr, char *buf) > +{ > + struct pmem_device *pmem = dev_to_disk(dev)->private_data; I want to say this should be dax_get_private()... However, looking at the use of dax_get_private() not a single caller checks for NULL! :-( So now I wonder why dax_get_private() exists... :-/ A quick history search does not make anything apparent. When the DAXDEV_ALIVE check was added to dax_get_private() no callers were changed to account for a potential NULL return. Dan? > + > + return sprintf(buf, "%d\n", !!dax_write_cache_enabled(pmem->dax_dev)); > +} > + > +static ssize_t write_cache_store(struct device *dev, > + struct device_attribute *attr, const char *buf, size_t len) > +{ > + struct pmem_device *pmem = dev_to_disk(dev)->private_data; Same here... Ira