Re: [PATCH v2] dax/bus: Upgrade resource conflict message to dev_err() in alloc_dax_region()

["Dan Williams" <djbw@kernel.org>]

On Tue, May 19, 2026, at 3:18 AM, Tomasz Wolski wrote:
> The dax_region resource conflict in alloc_dax_region() indicates a
> serious configuration problem — two subsystems (e.g. dax_hmem and
> dax_cxl) are attempting to register overlapping address ranges. This is
> not a transient or debug-level condition; it represents a genuine
> resource conflict that an administrator needs to be aware of.
>
> Switch from request_resource() + dev_dbg() to
> request_resource_conflict() + dev_err() so that the conflict is visible
> by default and the colliding resource is identified in the message.
>
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Link: 
> https://lore.kernel.org/linux-cxl/69c1a8d1c0fa9_7ee3100a1@dwillia2-mobl4.notmuch/
> Signed-off-by: Tomasz Wolski <tomasz.wolski@fujitsu.com>
> ---
>  drivers/dax/bus.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> index 68437c05e21d..66413c6c2ba0 100644
> --- a/drivers/dax/bus.c
> +++ b/drivers/dax/bus.c
> @@ -637,7 +637,7 @@ struct dax_region *alloc_dax_region(struct device 
> *parent, int region_id,
>  		unsigned long flags)
>  {
>  	struct dax_region *dax_region;
> -	int rc;
> +	struct resource *conflict;
> 
>  	/*
>  	 * The DAX core assumes that it can store its private data in
> @@ -670,10 +670,11 @@ struct dax_region *alloc_dax_region(struct device 
> *parent, int region_id,
>  		.flags = IORESOURCE_MEM | flags,
>  	};
> 
> -	rc = request_resource(&dax_regions, &dax_region->res);
> -	if (rc) {
> -		dev_dbg(parent, "dax_region resource conflict for %pR\n",
> -			&dax_region->res);
> +	conflict = request_resource_conflict(&dax_regions, &dax_region->res);

Just report the request_resource() failure. This case does not warrant exporting request_resource _conflict(). Historically one driver can not mess with another driver's resource beyond conflict detection.