[PATCH v6 5/9] dax: Track all dax_region allocations under a global resource tree

Smita Koralahalli
2026-02-10T06:45:24Z

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.

Co-developed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
---
drivers/dax/bus.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index fde29e0ad68b..5f387feb95f0 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);

/*
@@ -625,6 +626,8 @@ static void dax_region_unregister(void *region)
{
struct dax_region *dax_region = region;

+ scoped_guard(rwsem_write, &dax_region_rwsem)
+ release_resource(&dax_region->res);
sysfs_remove_groups(&dax_region->dev->kobj,
dax_region_attribute_groups);
dax_region_put(dax_region);
@@ -635,6 +638,7 @@ 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 +671,27 @@ 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)) {
- kfree(dax_region);
- return NULL;
+ scoped_guard(rwsem_write, &dax_region_rwsem)
+ 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:
+ scoped_guard(rwsem_write, &dax_region_rwsem)
+ release_resource(&dax_region->res);
+err_res:
+ kfree(dax_region);
+ return NULL;
}
EXPORT_SYMBOL_GPL(alloc_dax_region);

--
2.17.1