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[PATCH v8 6/9] dax: Track all dax_region allocations under a global resource tree

Smita Koralahalli posted 9 patches 1 week, 6 days ago
[PATCH v8 6/9] dax: Track all dax_region allocations under a global resource tree
Posted by Smita Koralahalli 1 week, 6 days ago 
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>
---
 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);
 
-- 
2.17.1
Re: [PATCH v8 6/9] dax: Track all dax_region allocations under a global resource tree
Posted by Dan Williams 1 week, 5 days ago 
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 <dan.j.williams@intel.com>
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
> ---
>  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");

Just type it out, skip using the DEFINE_RES* macro, like the definitions
of iomem_resource and soft_reserve_resource. Since the argument is a
size not an end address.

>  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);

I normally do not like a driver to be chatty, but resource conflicts are
significant. This one deserves to be dev_err().
Re: [PATCH v8 6/9] dax: Track all dax_region allocations under a global resource tree
Posted by Dave Jiang 1 week, 5 days ago 

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 <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>

> ---
>  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);
>

Patchew 2.1-devel-ea86937

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