[PATCH v2 5/8] lib/memregion: Uplevel the pmem "region" ida to a global allocator

[Dan Williams]

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.

Cc: Keith Busch <keith.bu...@intel.com>
Cc: Matthew Wilcox <wi...@infradead.org>
Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
---
 drivers/nvdimm/Kconfig       |    1 +
 drivers/nvdimm/core.c        |    1 -
 drivers/nvdimm/nd-core.h     |    1 -
 drivers/nvdimm/region_devs.c |   13 ++++---------
 include/linux/memregion.h    |    8 ++++++++
 lib/Kconfig                  |    7 +++++++
 lib/Makefile                 |    1 +
 lib/memregion.c              |   15 +++++++++++++++
 8 files changed, 36 insertions(+), 11 deletions(-)
 create mode 100644 include/linux/memregion.h
 create mode 100644 lib/memregion.c

diff --git a/drivers/nvdimm/Kconfig b/drivers/nvdimm/Kconfig
index 54500798f23a..4b3e66fe61c1 100644
--- a/drivers/nvdimm/Kconfig
+++ b/drivers/nvdimm/Kconfig
@@ -4,6 +4,7 @@ menuconfig LIBNVDIMM
        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
diff --git a/drivers/nvdimm/core.c b/drivers/nvdimm/core.c
index acce050856a8..75fe651d327d 100644
--- a/drivers/nvdimm/core.c
+++ b/drivers/nvdimm/core.c
@@ -463,7 +463,6 @@ static __exit void libnvdimm_exit(void)
        nd_region_exit();
        nvdimm_exit();
        nvdimm_bus_exit();
-       nd_region_devs_exit();
        nvdimm_devs_exit();
 }
 
diff --git a/drivers/nvdimm/nd-core.h b/drivers/nvdimm/nd-core.h
index e5ffd5733540..17561302dfec 100644
--- a/drivers/nvdimm/nd-core.h
+++ b/drivers/nvdimm/nd-core.h
@@ -133,7 +133,6 @@ struct nvdimm_bus *walk_to_nvdimm_bus(struct device 
*nd_dev);
 int __init nvdimm_bus_init(void);
 void nvdimm_bus_exit(void);
 void nvdimm_devs_exit(void);
-void nd_region_devs_exit(void);
 void nd_region_probe_success(struct nvdimm_bus *nvdimm_bus, struct device 
*dev);
 struct nd_region;
 void nd_region_create_ns_seed(struct nd_region *nd_region);
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index b4ef7d9ff22e..9e070363ff70 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -11,6 +11,7 @@
  * General Public License for more details.
  */
 #include <linux/scatterlist.h>
+#include <linux/memregion.h>
 #include <linux/highmem.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
@@ -27,7 +28,6 @@
  */
 #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,
@@ -141,7 +141,7 @@ static void nd_region_release(struct device *dev)
                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
@@ -1036,7 +1036,7 @@ static struct nd_region *nd_region_create(struct 
nvdimm_bus *nvdimm_bus,
 
        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;
 
@@ -1090,7 +1090,7 @@ static struct nd_region *nd_region_create(struct 
nvdimm_bus *nvdimm_bus,
        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;
@@ -1237,8 +1237,3 @@ int nd_region_conflict(struct nd_region *nd_region, 
resource_size_t start,
 
        return device_for_each_child(&nvdimm_bus->dev, &ctx, region_conflict);
 }
-
-void __exit nd_region_devs_exit(void)
-{
-       ida_destroy(&region_ida);
-}
diff --git a/include/linux/memregion.h b/include/linux/memregion.h
new file mode 100644
index 000000000000..ba03c70f98d2
--- /dev/null
+++ b/include/linux/memregion.h
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef _MEMREGION_H_
+#define _MEMREGION_H_
+#include <linux/types.h>
+
+int memregion_alloc(gfp_t gfp);
+void memregion_free(int id);
+#endif /* _MEMREGION_H_ */
diff --git a/lib/Kconfig b/lib/Kconfig
index 90623a0e1942..68621a0505a6 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -335,6 +335,13 @@ config DECOMPRESS_LZ4
 config GENERIC_ALLOCATOR
        bool
 
+#
+# Memory Region ID allocation for persistent memory and "specific
+# purpose" / performance differentiated memory ranges.
+#
+config MEMREGION
+       bool
+
 #
 # reed solomon support is select'ed if needed
 #
diff --git a/lib/Makefile b/lib/Makefile
index fb7697031a79..58cf99f68f36 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -136,6 +136,7 @@ obj-$(CONFIG_LIBCRC32C)     += libcrc32c.o
 obj-$(CONFIG_CRC8)     += crc8.o
 obj-$(CONFIG_XXHASH)   += xxhash.o
 obj-$(CONFIG_GENERIC_ALLOCATOR) += genalloc.o
+obj-$(CONFIG_MEMREGION) += memregion.o
 
 obj-$(CONFIG_842_COMPRESS) += 842/
 obj-$(CONFIG_842_DECOMPRESS) += 842/
diff --git a/lib/memregion.c b/lib/memregion.c
new file mode 100644
index 000000000000..f6c6a94c7921
--- /dev/null
+++ b/lib/memregion.c
@@ -0,0 +1,15 @@
+#include <linux/idr.h>
+
+static DEFINE_IDA(region_ids);
+
+int memregion_alloc(gfp_t gfp)
+{
+       return ida_alloc(&region_ids, gfp);
+}
+EXPORT_SYMBOL(memregion_alloc);
+
+void memregion_free(int id)
+{
+       ida_free(&region_ids, id);
+}
+EXPORT_SYMBOL(memregion_free);