device-dax: use the dev_pagemap internal refcount

The functionality is identical to the one currently open coded in
device-dax.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/dax/dax-private.h

@@ -43,8 +43,6 @@ struct dax_region {
  * @target_node: effective numa node if dev_dax memory range is onlined
  * @dev - device core
  * @pgmap - pgmap for memmap setup / lifetime (driver owned)
- * @ref: pgmap reference count (driver owned)
- * @cmp: @ref final put completion (driver owned)
  */
 struct dev_dax {
 	struct dax_region *region;
@@ -52,8 +50,6 @@ struct dev_dax {
 	int target_node;
 	struct device dev;
 	struct dev_pagemap pgmap;
-	struct percpu_ref ref;
-	struct completion cmp;
 };
 
 static inline struct dev_dax *to_dev_dax(struct device *dev)

drivers/dax/device.c

@@ -14,36 +14,6 @@
 #include "dax-private.h"
 #include "bus.h"
 
-static struct dev_dax *ref_to_dev_dax(struct percpu_ref *ref)
-{
-	return container_of(ref, struct dev_dax, ref);
-}
-
-static void dev_dax_percpu_release(struct percpu_ref *ref)
-{
-	struct dev_dax *dev_dax = ref_to_dev_dax(ref);
-
-	dev_dbg(&dev_dax->dev, "%s\n", __func__);
-	complete(&dev_dax->cmp);
-}
-
-static void dev_dax_percpu_exit(struct dev_pagemap *pgmap)
-{
-	struct dev_dax *dev_dax = container_of(pgmap, struct dev_dax, pgmap);
-
-	dev_dbg(&dev_dax->dev, "%s\n", __func__);
-	wait_for_completion(&dev_dax->cmp);
-	percpu_ref_exit(pgmap->ref);
-}
-
-static void dev_dax_percpu_kill(struct dev_pagemap *pgmap)
-{
-	struct dev_dax *dev_dax = container_of(pgmap, struct dev_dax, pgmap);
-
-	dev_dbg(&dev_dax->dev, "%s\n", __func__);
-	percpu_ref_kill(pgmap->ref);
-}
-
 static int check_vma(struct dev_dax *dev_dax, struct vm_area_struct *vma,
 		const char *func)
 {
@@ -441,11 +411,6 @@ static void dev_dax_kill(void *dev_dax)
 	kill_dev_dax(dev_dax);
 }
 
-static const struct dev_pagemap_ops dev_dax_pagemap_ops = {
-	.kill		= dev_dax_percpu_kill,
-	.cleanup	= dev_dax_percpu_exit,
-};
-
 int dev_dax_probe(struct device *dev)
 {
 	struct dev_dax *dev_dax = to_dev_dax(dev);
@@ -463,15 +428,7 @@ int dev_dax_probe(struct device *dev)
 		return -EBUSY;
 	}
 
-	init_completion(&dev_dax->cmp);
-	rc = percpu_ref_init(&dev_dax->ref, dev_dax_percpu_release, 0,
-			GFP_KERNEL);
-	if (rc)
-		return rc;
-
-	dev_dax->pgmap.ref = &dev_dax->ref;
 	dev_dax->pgmap.type = MEMORY_DEVICE_DEVDAX;
-	dev_dax->pgmap.ops = &dev_dax_pagemap_ops;
 	addr = devm_memremap_pages(dev, &dev_dax->pgmap);
 	if (IS_ERR(addr))
 		return PTR_ERR(addr);