dax: Track all dax_region allocations under a global resource tree

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 <dan.j.williams@intel.com>
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260322195343.206900-7-Smita.KoralahalliChannabasappa@amd.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 299134c9b2946c20e02da6f84c1c8a5015f6d67b..68437c05e21d74767c6b0a5e088c9ca5079b25e1 100644 (file)
--- 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);