lib: Uplevel the pmem "region" ida to a global allocator

In preparation for handling platform differentiated memory types beyond
persistent memory, uplevel the "region" identifier to a global number
space. This enables a device-dax instance to be registered to any memory
type with guaranteed unique names.

Signed-off-by: Dan Williams <[e-mail]>
Acked-by: Thomas Gleixner <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/nvdimm/Kconfig

···
 	depends on PHYS_ADDR_T_64BIT
 	depends on HAS_IOMEM
 	depends on BLK_DEV
+	select MEMREGION
 	help
 	  Generic support for non-volatile memory devices including
 	  ACPI-6-NFIT defined resources.  On platforms that define an

drivers/nvdimm/core.c

···
 	nd_region_exit();
 	nvdimm_exit();
 	nvdimm_bus_exit();
-	nd_region_devs_exit();
 	nvdimm_devs_exit();
 }
 

drivers/nvdimm/nd-core.h

···
 int __init nvdimm_bus_init(void);
 void nvdimm_bus_exit(void);
 void nvdimm_devs_exit(void);
-void nd_region_devs_exit(void);
 struct nd_region;
 void nd_region_advance_seeds(struct nd_region *nd_region, struct device *dev);
 void nd_region_create_ns_seed(struct nd_region *nd_region);

drivers/nvdimm/region_devs.c

···
  * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
  */
 #include <linux/scatterlist.h>
+#include <linux/memregion.h>
 #include <linux/highmem.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
···
  */
 #include <linux/io-64-nonatomic-hi-lo.h>
 
-static DEFINE_IDA(region_ida);
 static DEFINE_PER_CPU(int, flush_idx);
 
 static int nvdimm_map_flush(struct device *dev, struct nvdimm *nvdimm, int dimm,
···
 		put_device(&nvdimm->dev);
 	}
 	free_percpu(nd_region->lane);
-	ida_simple_remove(&region_ida, nd_region->id);
+	memregion_free(nd_region->id);
 	if (is_nd_blk(dev))
 		kfree(to_nd_blk_region(dev));
 	else
···
 
 	if (!region_buf)
 		return NULL;
-	nd_region->id = ida_simple_get(&region_ida, 0, 0, GFP_KERNEL);
+	nd_region->id = memregion_alloc(GFP_KERNEL);
 	if (nd_region->id < 0)
 		goto err_id;
 
···
 	return nd_region;
 
  err_percpu:
-	ida_simple_remove(&region_ida, nd_region->id);
+	memregion_free(nd_region->id);
  err_id:
 	kfree(region_buf);
 	return NULL;
···
 	};
 
 	return device_for_each_child(&nvdimm_bus->dev, &ctx, region_conflict);
-}
-
-void __exit nd_region_devs_exit(void)
-{
-	ida_destroy(&region_ida);
 }

include/linux/memregion.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _MEMREGION_H_
+#define _MEMREGION_H_
+#include <linux/types.h>
+#include <linux/errno.h>
+
+#ifdef CONFIG_MEMREGION
+int memregion_alloc(gfp_t gfp);
+void memregion_free(int id);
+#else
+static inline int memregion_alloc(gfp_t gfp)
+{
+	return -ENOMEM;
+}
+void memregion_free(int id)
+{
+}
+#endif
+#endif /* _MEMREGION_H_ */

lib/Kconfig

···
 config ARCH_HAS_PMEM_API
 	bool
 
+config MEMREGION
+	bool
+
 # use memcpy to implement user copies for nommu architectures
 config UACCESS_MEMCPY
 	bool

lib/Makefile

···
 
 obj-$(CONFIG_SG_SPLIT) += sg_split.o
 obj-$(CONFIG_SG_POOL) += sg_pool.o
+obj-$(CONFIG_MEMREGION) += memregion.o
 obj-$(CONFIG_STMP_DEVICE) += stmp_device.o
 obj-$(CONFIG_IRQ_POLL) += irq_poll.o
 

lib/memregion.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/* identifiers for device / performance-differentiated memory regions */
+#include <linux/idr.h>
+#include <linux/types.h>
+
+static DEFINE_IDA(memregion_ids);
+
+int memregion_alloc(gfp_t gfp)
+{
+	return ida_alloc(&memregion_ids, gfp);
+}
+EXPORT_SYMBOL(memregion_alloc);
+
+void memregion_free(int id)
+{
+	ida_free(&memregion_ids, id);
+}
+EXPORT_SYMBOL(memregion_free);