On 3/22/26 12:53 PM, Smita Koralahalli wrote:
> Introduce a global "DAX Regions" resource root and register each
> dax_region->res under it via request_resource(). Release the resource on
> dax_region teardown.
>
> By enforcing a single global namespace for dax_region allocations, this
> ensures only one of dax_hmem or dax_cxl can successfully register a
> dax_region for a given range.
>
> Suggested-by: Dan Williams <[email protected]>
> Signed-off-by: Smita Koralahalli <[email protected]>
> Reviewed-by: Jonathan Cameron <[email protected]>
Reviewed-by: Dave Jiang <[email protected]>
> ---
> drivers/dax/bus.c | 20 +++++++++++++++++---
> 1 file changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> index 299134c9b294..68437c05e21d 100644
> --- a/drivers/dax/bus.c
> +++ b/drivers/dax/bus.c
> @@ -10,6 +10,7 @@
> #include "dax-private.h"
> #include "bus.h"
>
> +static struct resource dax_regions = DEFINE_RES_MEM_NAMED(0, -1, "DAX
> Regions");
> static DEFINE_MUTEX(dax_bus_lock);
>
> /*
> @@ -627,6 +628,7 @@ static void dax_region_unregister(void *region)
>
> sysfs_remove_groups(&dax_region->dev->kobj,
> dax_region_attribute_groups);
> + release_resource(&dax_region->res);
> dax_region_put(dax_region);
> }
>
> @@ -635,6 +637,7 @@ struct dax_region *alloc_dax_region(struct device
> *parent, int region_id,
> unsigned long flags)
> {
> struct dax_region *dax_region;
> + int rc;
>
> /*
> * The DAX core assumes that it can store its private data in
> @@ -667,14 +670,25 @@ struct dax_region *alloc_dax_region(struct device
> *parent, int region_id,
> .flags = IORESOURCE_MEM | flags,
> };
>
> - if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups)) {
> - dax_region_put(dax_region);
> - return NULL;
> + rc = request_resource(&dax_regions, &dax_region->res);
> + if (rc) {
> + dev_dbg(parent, "dax_region resource conflict for %pR\n",
> + &dax_region->res);
> + goto err_res;
> }
>
> + if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups))
> + goto err_sysfs;
> +
> if (devm_add_action_or_reset(parent, dax_region_unregister, dax_region))
> return NULL;
> return dax_region;
> +
> +err_sysfs:
> + release_resource(&dax_region->res);
> +err_res:
> + dax_region_put(dax_region);
> + return NULL;
> }
> EXPORT_SYMBOL_GPL(alloc_dax_region);
>
