linux-kernel - Re: [PATCH] DAX: warn when kmem regions are truncated for memory block alignment.

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Message-ID: <Z-v7waimV3OZq_1H@gourry-fedora-PF4VCD3F>
Date: Tue, 1 Apr 2025 10:44:17 -0400
From: Gregory Price <gourry@...rry.net>
To: David Hildenbrand <david@...hat.com>
Cc: linux-cxl@...r.kernel.org, nvdimm@...ts.linux.dev,
	linux-kernel@...r.kernel.org, kernel-team@...a.com,
	dan.j.williams@...el.com, vishal.l.verma@...el.com,
	dave.jiang@...el.com
Subject: Re: [PATCH] DAX: warn when kmem regions are truncated for memory
 block alignment.

On Tue, Apr 01, 2025 at 11:47:32AM +0200, David Hildenbrand wrote:
> 
> Can't that be done a bit simpler?

Yes, this is better, lets do this.  Thank you!

> 
> 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);
>         }
>         init_node_memory_type(numa_node, mtype);
> 
> 
> -- 
> Cheers,
> 
> David / dhildenb
>