On Tue, Apr 01, 2025 at 10:47:09AM -0700, Dan Williams wrote:
> David Hildenbrand wrote:
> > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> > index e97d47f42ee2e..23a68ff809cdf 100644
> > --- a/drivers/dax/kmem.c
> > +++ b/drivers/dax/kmem.c
> > @@ -67,8 +67,8 @@ static void kmem_put_memory_types(void)
> >
> > static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
> > {
> > + unsigned long total_len = 0, orig_len = 0;
> > struct device *dev = &dev_dax->dev;
> > - unsigned long total_len = 0;
> > struct dax_kmem_data *data;
> > struct memory_dev_type *mtype;
> > int i, rc, mapped = 0;
> > @@ -97,6 +97,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
> > for (i = 0; i < dev_dax->nr_range; i++) {
> > struct range range;
> >
> > + orig_len += range_len(&dev_dax->ranges[i].range);
> > rc = dax_kmem_range(dev_dax, i, &range);
> > if (rc) {
> > dev_info(dev, "mapping%d: %#llx-%#llx too small
> > after alignment\n",
> > @@ -109,6 +110,9 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
> > if (!total_len) {
> > dev_warn(dev, "rejecting DAX region without any memory
> > after alignment\n");
> > return -EINVAL;
> > + } else if (total_len != orig_len) {
> > + dev_warn(dev, "DAX region truncated by %lu bytes due to
> > alignment\n",
> > + orig_len - total_len);
>
> This looks good, I agree with it being a warn because the user has lost
> usable capacity and maybe this eventually pressures platform BIOS to
> avoid causing Linux warnings.
>
> In terms of making that loss easier for people to report / understand
> how about use string_get_size() to convert raw bytes to power of 10 and
> power of 2 values? I.e.
>
> "DAX region truncated by X.XX GiB (Y.YY GB) due to alignment."
Will pick this up in v2.
