Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

14 files changed, 3417 insertions, 0 deletions

diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
new file mode 100644
index 000000000..5fdf269a8
--- /dev/null
+++ b/drivers/dax/Kconfig
@@ -0,0 +1,69 @@
+# SPDX-License-Identifier: GPL-2.0-only
+menuconfig DAX
+	tristate "DAX: direct access to differentiated memory"
+	select SRCU
+	default m if NVDIMM_DAX
+
+if DAX
+
+config DEV_DAX
+	tristate "Device DAX: direct access mapping device"
+	depends on TRANSPARENT_HUGEPAGE
+	help
+	  Support raw access to differentiated (persistence, bandwidth,
+	  latency...) memory via an mmap(2) capable character
+	  device.  Platform firmware or a device driver may identify a
+	  platform memory resource that is differentiated from the
+	  baseline memory pool.  Mappings of a /dev/daxX.Y device impose
+	  restrictions that make the mapping behavior deterministic.
+
+config DEV_DAX_PMEM
+	tristate "PMEM DAX: direct access to persistent memory"
+	depends on LIBNVDIMM && NVDIMM_DAX && DEV_DAX
+	default DEV_DAX
+	help
+	  Support raw access to persistent memory.  Note that this
+	  driver consumes memory ranges allocated and exported by the
+	  libnvdimm sub-system.
+
+	  Say M if unsure
+
+config DEV_DAX_HMEM
+	tristate "HMEM DAX: direct access to 'specific purpose' memory"
+	depends on EFI_SOFT_RESERVE
+	select NUMA_KEEP_MEMINFO if (NUMA && X86)
+	default DEV_DAX
+	help
+	  EFI 2.8 platforms, and others, may advertise 'specific purpose'
+	  memory. For example, a high bandwidth memory pool. The
+	  indication from platform firmware is meant to reserve the
+	  memory from typical usage by default. This driver creates
+	  device-dax instances for these memory ranges, and that also
+	  enables the possibility to assign them to the DEV_DAX_KMEM
+	  driver to override the reservation and add them to kernel
+	  "System RAM" pool.
+
+	  Say M if unsure.
+
+config DEV_DAX_HMEM_DEVICES
+	depends on DEV_DAX_HMEM && DAX=y
+	def_bool y
+
+config DEV_DAX_KMEM
+	tristate "KMEM DAX: volatile-use of persistent memory"
+	default DEV_DAX
+	depends on DEV_DAX
+	depends on MEMORY_HOTPLUG # for add_memory() and friends
+	help
+	  Support access to persistent, or other performance
+	  differentiated memory as if it were System RAM. This allows
+	  easier use of persistent memory by unmodified applications, or
+	  adds core kernel memory services to heterogeneous memory types
+	  (HMEM) marked "reserved" by platform firmware.
+
+	  To use this feature, a DAX device must be unbound from the
+	  device_dax driver and bound to this kmem driver on each boot.
+
+	  Say N if unsure.
+
+endif
diff --git a/drivers/dax/Makefile b/drivers/dax/Makefile
new file mode 100644
index 000000000..90a56ca3b
--- /dev/null
+++ b/drivers/dax/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_DAX) += dax.o
+obj-$(CONFIG_DEV_DAX) += device_dax.o
+obj-$(CONFIG_DEV_DAX_KMEM) += kmem.o
+obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem.o
+
+dax-y := super.o
+dax-y += bus.o
+device_dax-y := device.o
+dax_pmem-y := pmem.o
+
+obj-y += hmem/
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
new file mode 100644
index 000000000..3a9348c7f
--- /dev/null
+++ b/drivers/dax/bus.c
@@ -0,0 +1,1499 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2017-2018 Intel Corporation. All rights reserved. */
+#include <linux/memremap.h>
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/dax.h>
+#include <linux/io.h>
+#include "dax-private.h"
+#include "bus.h"
+
+static DEFINE_MUTEX(dax_bus_lock);
+
+#define DAX_NAME_LEN 30
+struct dax_id {
+	struct list_head list;
+	char dev_name[DAX_NAME_LEN];
+};
+
+static int dax_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	/*
+	 * We only ever expect to handle device-dax instances, i.e. the
+	 * @type argument to MODULE_ALIAS_DAX_DEVICE() is always zero
+	 */
+	return add_uevent_var(env, "MODALIAS=" DAX_DEVICE_MODALIAS_FMT, 0);
+}
+
+static struct dax_device_driver *to_dax_drv(struct device_driver *drv)
+{
+	return container_of(drv, struct dax_device_driver, drv);
+}
+
+static struct dax_id *__dax_match_id(struct dax_device_driver *dax_drv,
+		const char *dev_name)
+{
+	struct dax_id *dax_id;
+
+	lockdep_assert_held(&dax_bus_lock);
+
+	list_for_each_entry(dax_id, &dax_drv->ids, list)
+		if (sysfs_streq(dax_id->dev_name, dev_name))
+			return dax_id;
+	return NULL;
+}
+
+static int dax_match_id(struct dax_device_driver *dax_drv, struct device *dev)
+{
+	int match;
+
+	mutex_lock(&dax_bus_lock);
+	match = !!__dax_match_id(dax_drv, dev_name(dev));
+	mutex_unlock(&dax_bus_lock);
+
+	return match;
+}
+
+enum id_action {
+	ID_REMOVE,
+	ID_ADD,
+};
+
+static ssize_t do_id_store(struct device_driver *drv, const char *buf,
+		size_t count, enum id_action action)
+{
+	struct dax_device_driver *dax_drv = to_dax_drv(drv);
+	unsigned int region_id, id;
+	char devname[DAX_NAME_LEN];
+	struct dax_id *dax_id;
+	ssize_t rc = count;
+	int fields;
+
+	fields = sscanf(buf, "dax%d.%d", &region_id, &id);
+	if (fields != 2)
+		return -EINVAL;
+	sprintf(devname, "dax%d.%d", region_id, id);
+	if (!sysfs_streq(buf, devname))
+		return -EINVAL;
+
+	mutex_lock(&dax_bus_lock);
+	dax_id = __dax_match_id(dax_drv, buf);
+	if (!dax_id) {
+		if (action == ID_ADD) {
+			dax_id = kzalloc(sizeof(*dax_id), GFP_KERNEL);
+			if (dax_id) {
+				strncpy(dax_id->dev_name, buf, DAX_NAME_LEN);
+				list_add(&dax_id->list, &dax_drv->ids);
+			} else
+				rc = -ENOMEM;
+		}
+	} else if (action == ID_REMOVE) {
+		list_del(&dax_id->list);
+		kfree(dax_id);
+	}
+	mutex_unlock(&dax_bus_lock);
+
+	if (rc < 0)
+		return rc;
+	if (action == ID_ADD)
+		rc = driver_attach(drv);
+	if (rc)
+		return rc;
+	return count;
+}
+
+static ssize_t new_id_store(struct device_driver *drv, const char *buf,
+		size_t count)
+{
+	return do_id_store(drv, buf, count, ID_ADD);
+}
+static DRIVER_ATTR_WO(new_id);
+
+static ssize_t remove_id_store(struct device_driver *drv, const char *buf,
+		size_t count)
+{
+	return do_id_store(drv, buf, count, ID_REMOVE);
+}
+static DRIVER_ATTR_WO(remove_id);
+
+static struct attribute *dax_drv_attrs[] = {
+	&driver_attr_new_id.attr,
+	&driver_attr_remove_id.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(dax_drv);
+
+static int dax_bus_match(struct device *dev, struct device_driver *drv);
+
+/*
+ * Static dax regions are regions created by an external subsystem
+ * nvdimm where a single range is assigned. Its boundaries are by the external
+ * subsystem and are usually limited to one physical memory range. For example,
+ * for PMEM it is usually defined by NVDIMM Namespace boundaries (i.e. a
+ * single contiguous range)
+ *
+ * On dynamic dax regions, the assigned region can be partitioned by dax core
+ * into multiple subdivisions. A subdivision is represented into one
+ * /dev/daxN.M device composed by one or more potentially discontiguous ranges.
+ *
+ * When allocating a dax region, drivers must set whether it's static
+ * (IORESOURCE_DAX_STATIC).  On static dax devices, the @pgmap is pre-assigned
+ * to dax core when calling devm_create_dev_dax(), whereas in dynamic dax
+ * devices it is NULL but afterwards allocated by dax core on device ->probe().
+ * Care is needed to make sure that dynamic dax devices are torn down with a
+ * cleared @pgmap field (see kill_dev_dax()).
+ */
+static bool is_static(struct dax_region *dax_region)
+{
+	return (dax_region->res.flags & IORESOURCE_DAX_STATIC) != 0;
+}
+
+bool static_dev_dax(struct dev_dax *dev_dax)
+{
+	return is_static(dev_dax->region);
+}
+EXPORT_SYMBOL_GPL(static_dev_dax);
+
+static u64 dev_dax_size(struct dev_dax *dev_dax)
+{
+	u64 size = 0;
+	int i;
+
+	device_lock_assert(&dev_dax->dev);
+
+	for (i = 0; i < dev_dax->nr_range; i++)
+		size += range_len(&dev_dax->ranges[i].range);
+
+	return size;
+}
+
+static int dax_bus_probe(struct device *dev)
+{
+	struct dax_device_driver *dax_drv = to_dax_drv(dev->driver);
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	struct dax_region *dax_region = dev_dax->region;
+	int rc;
+
+	if (dev_dax_size(dev_dax) == 0 || dev_dax->id < 0)
+		return -ENXIO;
+
+	rc = dax_drv->probe(dev_dax);
+
+	if (rc || is_static(dax_region))
+		return rc;
+
+	/*
+	 * Track new seed creation only after successful probe of the
+	 * previous seed.
+	 */
+	if (dax_region->seed == dev)
+		dax_region->seed = NULL;
+
+	return 0;
+}
+
+static void dax_bus_remove(struct device *dev)
+{
+	struct dax_device_driver *dax_drv = to_dax_drv(dev->driver);
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+
+	if (dax_drv->remove)
+		dax_drv->remove(dev_dax);
+}
+
+static struct bus_type dax_bus_type = {
+	.name = "dax",
+	.uevent = dax_bus_uevent,
+	.match = dax_bus_match,
+	.probe = dax_bus_probe,
+	.remove = dax_bus_remove,
+	.drv_groups = dax_drv_groups,
+};
+
+static int dax_bus_match(struct device *dev, struct device_driver *drv)
+{
+	struct dax_device_driver *dax_drv = to_dax_drv(drv);
+
+	/*
+	 * All but the 'device-dax' driver, which has 'match_always'
+	 * set, requires an exact id match.
+	 */
+	if (dax_drv->match_always)
+		return 1;
+
+	return dax_match_id(dax_drv, dev);
+}
+
+/*
+ * Rely on the fact that drvdata is set before the attributes are
+ * registered, and that the attributes are unregistered before drvdata
+ * is cleared to assume that drvdata is always valid.
+ */
+static ssize_t id_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", dax_region->id);
+}
+static DEVICE_ATTR_RO(id);
+
+static ssize_t region_size_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%llu\n", (unsigned long long)
+			resource_size(&dax_region->res));
+}
+static struct device_attribute dev_attr_region_size = __ATTR(size, 0444,
+		region_size_show, NULL);
+
+static ssize_t region_align_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", dax_region->align);
+}
+static struct device_attribute dev_attr_region_align =
+		__ATTR(align, 0400, region_align_show, NULL);
+
+#define for_each_dax_region_resource(dax_region, res) \
+	for (res = (dax_region)->res.child; res; res = res->sibling)
+
+static unsigned long long dax_region_avail_size(struct dax_region *dax_region)
+{
+	resource_size_t size = resource_size(&dax_region->res);
+	struct resource *res;
+
+	device_lock_assert(dax_region->dev);
+
+	for_each_dax_region_resource(dax_region, res)
+		size -= resource_size(res);
+	return size;
+}
+
+static ssize_t available_size_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+	unsigned long long size;
+
+	device_lock(dev);
+	size = dax_region_avail_size(dax_region);
+	device_unlock(dev);
+
+	return sprintf(buf, "%llu\n", size);
+}
+static DEVICE_ATTR_RO(available_size);
+
+static ssize_t seed_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+	struct device *seed;
+	ssize_t rc;
+
+	if (is_static(dax_region))
+		return -EINVAL;
+
+	device_lock(dev);
+	seed = dax_region->seed;
+	rc = sprintf(buf, "%s\n", seed ? dev_name(seed) : "");
+	device_unlock(dev);
+
+	return rc;
+}
+static DEVICE_ATTR_RO(seed);
+
+static ssize_t create_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+	struct device *youngest;
+	ssize_t rc;
+
+	if (is_static(dax_region))
+		return -EINVAL;
+
+	device_lock(dev);
+	youngest = dax_region->youngest;
+	rc = sprintf(buf, "%s\n", youngest ? dev_name(youngest) : "");
+	device_unlock(dev);
+
+	return rc;
+}
+
+static ssize_t create_store(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t len)
+{
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+	unsigned long long avail;
+	ssize_t rc;
+	int val;
+
+	if (is_static(dax_region))
+		return -EINVAL;
+
+	rc = kstrtoint(buf, 0, &val);
+	if (rc)
+		return rc;
+	if (val != 1)
+		return -EINVAL;
+
+	device_lock(dev);
+	avail = dax_region_avail_size(dax_region);
+	if (avail == 0)
+		rc = -ENOSPC;
+	else {
+		struct dev_dax_data data = {
+			.dax_region = dax_region,
+			.size = 0,
+			.id = -1,
+		};
+		struct dev_dax *dev_dax = devm_create_dev_dax(&data);
+
+		if (IS_ERR(dev_dax))
+			rc = PTR_ERR(dev_dax);
+		else {
+			/*
+			 * In support of crafting multiple new devices
+			 * simultaneously multiple seeds can be created,
+			 * but only the first one that has not been
+			 * successfully bound is tracked as the region
+			 * seed.
+			 */
+			if (!dax_region->seed)
+				dax_region->seed = &dev_dax->dev;
+			dax_region->youngest = &dev_dax->dev;
+			rc = len;
+		}
+	}
+	device_unlock(dev);
+
+	return rc;
+}
+static DEVICE_ATTR_RW(create);
+
+void kill_dev_dax(struct dev_dax *dev_dax)
+{
+	struct dax_device *dax_dev = dev_dax->dax_dev;
+	struct inode *inode = dax_inode(dax_dev);
+
+	kill_dax(dax_dev);
+	unmap_mapping_range(inode->i_mapping, 0, 0, 1);
+
+	/*
+	 * Dynamic dax region have the pgmap allocated via dev_kzalloc()
+	 * and thus freed by devm. Clear the pgmap to not have stale pgmap
+	 * ranges on probe() from previous reconfigurations of region devices.
+	 */
+	if (!static_dev_dax(dev_dax))
+		dev_dax->pgmap = NULL;
+}
+EXPORT_SYMBOL_GPL(kill_dev_dax);
+
+static void trim_dev_dax_range(struct dev_dax *dev_dax)
+{
+	int i = dev_dax->nr_range - 1;
+	struct range *range = &dev_dax->ranges[i].range;
+	struct dax_region *dax_region = dev_dax->region;
+
+	device_lock_assert(dax_region->dev);
+	dev_dbg(&dev_dax->dev, "delete range[%d]: %#llx:%#llx\n", i,
+		(unsigned long long)range->start,
+		(unsigned long long)range->end);
+
+	__release_region(&dax_region->res, range->start, range_len(range));
+	if (--dev_dax->nr_range == 0) {
+		kfree(dev_dax->ranges);
+		dev_dax->ranges = NULL;
+	}
+}
+
+static void free_dev_dax_ranges(struct dev_dax *dev_dax)
+{
+	while (dev_dax->nr_range)
+		trim_dev_dax_range(dev_dax);
+}
+
+static void unregister_dev_dax(void *dev)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+
+	dev_dbg(dev, "%s\n", __func__);
+
+	kill_dev_dax(dev_dax);
+	device_del(dev);
+	free_dev_dax_ranges(dev_dax);
+	put_device(dev);
+}
+
+static void dax_region_free(struct kref *kref)
+{
+	struct dax_region *dax_region;
+
+	dax_region = container_of(kref, struct dax_region, kref);
+	kfree(dax_region);
+}
+
+void dax_region_put(struct dax_region *dax_region)
+{
+	kref_put(&dax_region->kref, dax_region_free);
+}
+EXPORT_SYMBOL_GPL(dax_region_put);
+
+/* a return value >= 0 indicates this invocation invalidated the id */
+static int __free_dev_dax_id(struct dev_dax *dev_dax)
+{
+	struct device *dev = &dev_dax->dev;
+	struct dax_region *dax_region;
+	int rc = dev_dax->id;
+
+	device_lock_assert(dev);
+
+	if (!dev_dax->dyn_id || dev_dax->id < 0)
+		return -1;
+	dax_region = dev_dax->region;
+	ida_free(&dax_region->ida, dev_dax->id);
+	dax_region_put(dax_region);
+	dev_dax->id = -1;
+	return rc;
+}
+
+static int free_dev_dax_id(struct dev_dax *dev_dax)
+{
+	struct device *dev = &dev_dax->dev;
+	int rc;
+
+	device_lock(dev);
+	rc = __free_dev_dax_id(dev_dax);
+	device_unlock(dev);
+	return rc;
+}
+
+static int alloc_dev_dax_id(struct dev_dax *dev_dax)
+{
+	struct dax_region *dax_region = dev_dax->region;
+	int id;
+
+	id = ida_alloc(&dax_region->ida, GFP_KERNEL);
+	if (id < 0)
+		return id;
+	kref_get(&dax_region->kref);
+	dev_dax->dyn_id = true;
+	dev_dax->id = id;
+	return id;
+}
+
+static ssize_t delete_store(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t len)
+{
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+	struct dev_dax *dev_dax;
+	struct device *victim;
+	bool do_del = false;
+	int rc;
+
+	if (is_static(dax_region))
+		return -EINVAL;
+
+	victim = device_find_child_by_name(dax_region->dev, buf);
+	if (!victim)
+		return -ENXIO;
+
+	device_lock(dev);
+	device_lock(victim);
+	dev_dax = to_dev_dax(victim);
+	if (victim->driver || dev_dax_size(dev_dax))
+		rc = -EBUSY;
+	else {
+		/*
+		 * Invalidate the device so it does not become active
+		 * again, but always preserve device-id-0 so that
+		 * /sys/bus/dax/ is guaranteed to be populated while any
+		 * dax_region is registered.
+		 */
+		if (dev_dax->id > 0) {
+			do_del = __free_dev_dax_id(dev_dax) >= 0;
+			rc = len;
+			if (dax_region->seed == victim)
+				dax_region->seed = NULL;
+			if (dax_region->youngest == victim)
+				dax_region->youngest = NULL;
+		} else
+			rc = -EBUSY;
+	}
+	device_unlock(victim);
+
+	/* won the race to invalidate the device, clean it up */
+	if (do_del)
+		devm_release_action(dev, unregister_dev_dax, victim);
+	device_unlock(dev);
+	put_device(victim);
+
+	return rc;
+}
+static DEVICE_ATTR_WO(delete);
+
+static umode_t dax_region_visible(struct kobject *kobj, struct attribute *a,
+		int n)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+
+	if (is_static(dax_region))
+		if (a == &dev_attr_available_size.attr
+				|| a == &dev_attr_create.attr
+				|| a == &dev_attr_seed.attr
+				|| a == &dev_attr_delete.attr)
+			return 0;
+	return a->mode;
+}
+
+static struct attribute *dax_region_attributes[] = {
+	&dev_attr_available_size.attr,
+	&dev_attr_region_size.attr,
+	&dev_attr_region_align.attr,
+	&dev_attr_create.attr,
+	&dev_attr_seed.attr,
+	&dev_attr_delete.attr,
+	&dev_attr_id.attr,
+	NULL,
+};
+
+static const struct attribute_group dax_region_attribute_group = {
+	.name = "dax_region",
+	.attrs = dax_region_attributes,
+	.is_visible = dax_region_visible,
+};
+
+static const struct attribute_group *dax_region_attribute_groups[] = {
+	&dax_region_attribute_group,
+	NULL,
+};
+
+static void dax_region_unregister(void *region)
+{
+	struct dax_region *dax_region = region;
+
+	sysfs_remove_groups(&dax_region->dev->kobj,
+			dax_region_attribute_groups);
+	dax_region_put(dax_region);
+}
+
+struct dax_region *alloc_dax_region(struct device *parent, int region_id,
+		struct range *range, int target_node, unsigned int align,
+		unsigned long flags)
+{
+	struct dax_region *dax_region;
+
+	/*
+	 * The DAX core assumes that it can store its private data in
+	 * parent->driver_data. This WARN is a reminder / safeguard for
+	 * developers of device-dax drivers.
+	 */
+	if (dev_get_drvdata(parent)) {
+		dev_WARN(parent, "dax core failed to setup private data\n");
+		return NULL;
+	}
+
+	if (!IS_ALIGNED(range->start, align)
+			|| !IS_ALIGNED(range_len(range), align))
+		return NULL;
+
+	dax_region = kzalloc(sizeof(*dax_region), GFP_KERNEL);
+	if (!dax_region)
+		return NULL;
+
+	dev_set_drvdata(parent, dax_region);
+	kref_init(&dax_region->kref);
+	dax_region->id = region_id;
+	dax_region->align = align;
+	dax_region->dev = parent;
+	dax_region->target_node = target_node;
+	ida_init(&dax_region->ida);
+	dax_region->res = (struct resource) {
+		.start = range->start,
+		.end = range->end,
+		.flags = IORESOURCE_MEM | flags,
+	};
+
+	if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups)) {
+		kfree(dax_region);
+		return NULL;
+	}
+
+	kref_get(&dax_region->kref);
+	if (devm_add_action_or_reset(parent, dax_region_unregister, dax_region))
+		return NULL;
+	return dax_region;
+}
+EXPORT_SYMBOL_GPL(alloc_dax_region);
+
+static void dax_mapping_release(struct device *dev)
+{
+	struct dax_mapping *mapping = to_dax_mapping(dev);
+	struct device *parent = dev->parent;
+	struct dev_dax *dev_dax = to_dev_dax(parent);
+
+	ida_free(&dev_dax->ida, mapping->id);
+	kfree(mapping);
+	put_device(parent);
+}
+
+static void unregister_dax_mapping(void *data)
+{
+	struct device *dev = data;
+	struct dax_mapping *mapping = to_dax_mapping(dev);
+	struct dev_dax *dev_dax = to_dev_dax(dev->parent);
+	struct dax_region *dax_region = dev_dax->region;
+
+	dev_dbg(dev, "%s\n", __func__);
+
+	device_lock_assert(dax_region->dev);
+
+	dev_dax->ranges[mapping->range_id].mapping = NULL;
+	mapping->range_id = -1;
+
+	device_del(dev);
+	put_device(dev);
+}
+
+static struct dev_dax_range *get_dax_range(struct device *dev)
+{
+	struct dax_mapping *mapping = to_dax_mapping(dev);
+	struct dev_dax *dev_dax = to_dev_dax(dev->parent);
+	struct dax_region *dax_region = dev_dax->region;
+
+	device_lock(dax_region->dev);
+	if (mapping->range_id < 0) {
+		device_unlock(dax_region->dev);
+		return NULL;
+	}
+
+	return &dev_dax->ranges[mapping->range_id];
+}
+
+static void put_dax_range(struct dev_dax_range *dax_range)
+{
+	struct dax_mapping *mapping = dax_range->mapping;
+	struct dev_dax *dev_dax = to_dev_dax(mapping->dev.parent);
+	struct dax_region *dax_region = dev_dax->region;
+
+	device_unlock(dax_region->dev);
+}
+
+static ssize_t start_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dev_dax_range *dax_range;
+	ssize_t rc;
+
+	dax_range = get_dax_range(dev);
+	if (!dax_range)
+		return -ENXIO;
+	rc = sprintf(buf, "%#llx\n", dax_range->range.start);
+	put_dax_range(dax_range);
+
+	return rc;
+}
+static DEVICE_ATTR(start, 0400, start_show, NULL);
+
+static ssize_t end_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dev_dax_range *dax_range;
+	ssize_t rc;
+
+	dax_range = get_dax_range(dev);
+	if (!dax_range)
+		return -ENXIO;
+	rc = sprintf(buf, "%#llx\n", dax_range->range.end);
+	put_dax_range(dax_range);
+
+	return rc;
+}
+static DEVICE_ATTR(end, 0400, end_show, NULL);
+
+static ssize_t pgoff_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dev_dax_range *dax_range;
+	ssize_t rc;
+
+	dax_range = get_dax_range(dev);
+	if (!dax_range)
+		return -ENXIO;
+	rc = sprintf(buf, "%#lx\n", dax_range->pgoff);
+	put_dax_range(dax_range);
+
+	return rc;
+}
+static DEVICE_ATTR(page_offset, 0400, pgoff_show, NULL);
+
+static struct attribute *dax_mapping_attributes[] = {
+	&dev_attr_start.attr,
+	&dev_attr_end.attr,
+	&dev_attr_page_offset.attr,
+	NULL,
+};
+
+static const struct attribute_group dax_mapping_attribute_group = {
+	.attrs = dax_mapping_attributes,
+};
+
+static const struct attribute_group *dax_mapping_attribute_groups[] = {
+	&dax_mapping_attribute_group,
+	NULL,
+};
+
+static struct device_type dax_mapping_type = {
+	.release = dax_mapping_release,
+	.groups = dax_mapping_attribute_groups,
+};
+
+static int devm_register_dax_mapping(struct dev_dax *dev_dax, int range_id)
+{
+	struct dax_region *dax_region = dev_dax->region;
+	struct dax_mapping *mapping;
+	struct device *dev;
+	int rc;
+
+	device_lock_assert(dax_region->dev);
+
+	if (dev_WARN_ONCE(&dev_dax->dev, !dax_region->dev->driver,
+				"region disabled\n"))
+		return -ENXIO;
+
+	mapping = kzalloc(sizeof(*mapping), GFP_KERNEL);
+	if (!mapping)
+		return -ENOMEM;
+	mapping->range_id = range_id;
+	mapping->id = ida_alloc(&dev_dax->ida, GFP_KERNEL);
+	if (mapping->id < 0) {
+		kfree(mapping);
+		return -ENOMEM;
+	}
+	dev_dax->ranges[range_id].mapping = mapping;
+	dev = &mapping->dev;
+	device_initialize(dev);
+	dev->parent = &dev_dax->dev;
+	get_device(dev->parent);
+	dev->type = &dax_mapping_type;
+	dev_set_name(dev, "mapping%d", mapping->id);
+	rc = device_add(dev);
+	if (rc) {
+		put_device(dev);
+		return rc;
+	}
+
+	rc = devm_add_action_or_reset(dax_region->dev, unregister_dax_mapping,
+			dev);
+	if (rc)
+		return rc;
+	return 0;
+}
+
+static int alloc_dev_dax_range(struct dev_dax *dev_dax, u64 start,
+		resource_size_t size)
+{
+	struct dax_region *dax_region = dev_dax->region;
+	struct resource *res = &dax_region->res;
+	struct device *dev = &dev_dax->dev;
+	struct dev_dax_range *ranges;
+	unsigned long pgoff = 0;
+	struct resource *alloc;
+	int i, rc;
+
+	device_lock_assert(dax_region->dev);
+
+	/* handle the seed alloc special case */
+	if (!size) {
+		if (dev_WARN_ONCE(dev, dev_dax->nr_range,
+					"0-size allocation must be first\n"))
+			return -EBUSY;
+		/* nr_range == 0 is elsewhere special cased as 0-size device */
+		return 0;
+	}
+
+	alloc = __request_region(res, start, size, dev_name(dev), 0);
+	if (!alloc)
+		return -ENOMEM;
+
+	ranges = krealloc(dev_dax->ranges, sizeof(*ranges)
+			* (dev_dax->nr_range + 1), GFP_KERNEL);
+	if (!ranges) {
+		__release_region(res, alloc->start, resource_size(alloc));
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < dev_dax->nr_range; i++)
+		pgoff += PHYS_PFN(range_len(&ranges[i].range));
+	dev_dax->ranges = ranges;
+	ranges[dev_dax->nr_range++] = (struct dev_dax_range) {
+		.pgoff = pgoff,
+		.range = {
+			.start = alloc->start,
+			.end = alloc->end,
+		},
+	};
+
+	dev_dbg(dev, "alloc range[%d]: %pa:%pa\n", dev_dax->nr_range - 1,
+			&alloc->start, &alloc->end);
+	/*
+	 * A dev_dax instance must be registered before mapping device
+	 * children can be added. Defer to devm_create_dev_dax() to add
+	 * the initial mapping device.
+	 */
+	if (!device_is_registered(&dev_dax->dev))
+		return 0;
+
+	rc = devm_register_dax_mapping(dev_dax, dev_dax->nr_range - 1);
+	if (rc)
+		trim_dev_dax_range(dev_dax);
+
+	return rc;
+}
+
+static int adjust_dev_dax_range(struct dev_dax *dev_dax, struct resource *res, resource_size_t size)
+{
+	int last_range = dev_dax->nr_range - 1;
+	struct dev_dax_range *dax_range = &dev_dax->ranges[last_range];
+	struct dax_region *dax_region = dev_dax->region;
+	bool is_shrink = resource_size(res) > size;
+	struct range *range = &dax_range->range;
+	struct device *dev = &dev_dax->dev;
+	int rc;
+
+	device_lock_assert(dax_region->dev);
+
+	if (dev_WARN_ONCE(dev, !size, "deletion is handled by dev_dax_shrink\n"))
+		return -EINVAL;
+
+	rc = adjust_resource(res, range->start, size);
+	if (rc)
+		return rc;
+
+	*range = (struct range) {
+		.start = range->start,
+		.end = range->start + size - 1,
+	};
+
+	dev_dbg(dev, "%s range[%d]: %#llx:%#llx\n", is_shrink ? "shrink" : "extend",
+			last_range, (unsigned long long) range->start,
+			(unsigned long long) range->end);
+
+	return 0;
+}
+
+static ssize_t size_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	unsigned long long size;
+
+	device_lock(dev);
+	size = dev_dax_size(dev_dax);
+	device_unlock(dev);
+
+	return sprintf(buf, "%llu\n", size);
+}
+
+static bool alloc_is_aligned(struct dev_dax *dev_dax, resource_size_t size)
+{
+	/*
+	 * The minimum mapping granularity for a device instance is a
+	 * single subsection, unless the arch says otherwise.
+	 */
+	return IS_ALIGNED(size, max_t(unsigned long, dev_dax->align, memremap_compat_align()));
+}
+
+static int dev_dax_shrink(struct dev_dax *dev_dax, resource_size_t size)
+{
+	resource_size_t to_shrink = dev_dax_size(dev_dax) - size;
+	struct dax_region *dax_region = dev_dax->region;
+	struct device *dev = &dev_dax->dev;
+	int i;
+
+	for (i = dev_dax->nr_range - 1; i >= 0; i--) {
+		struct range *range = &dev_dax->ranges[i].range;
+		struct dax_mapping *mapping = dev_dax->ranges[i].mapping;
+		struct resource *adjust = NULL, *res;
+		resource_size_t shrink;
+
+		shrink = min_t(u64, to_shrink, range_len(range));
+		if (shrink >= range_len(range)) {
+			devm_release_action(dax_region->dev,
+					unregister_dax_mapping, &mapping->dev);
+			trim_dev_dax_range(dev_dax);
+			to_shrink -= shrink;
+			if (!to_shrink)
+				break;
+			continue;
+		}
+
+		for_each_dax_region_resource(dax_region, res)
+			if (strcmp(res->name, dev_name(dev)) == 0
+					&& res->start == range->start) {
+				adjust = res;
+				break;
+			}
+
+		if (dev_WARN_ONCE(dev, !adjust || i != dev_dax->nr_range - 1,
+					"failed to find matching resource\n"))
+			return -ENXIO;
+		return adjust_dev_dax_range(dev_dax, adjust, range_len(range)
+				- shrink);
+	}
+	return 0;
+}
+
+/*
+ * Only allow adjustments that preserve the relative pgoff of existing
+ * allocations. I.e. the dev_dax->ranges array is ordered by increasing pgoff.
+ */
+static bool adjust_ok(struct dev_dax *dev_dax, struct resource *res)
+{
+	struct dev_dax_range *last;
+	int i;
+
+	if (dev_dax->nr_range == 0)
+		return false;
+	if (strcmp(res->name, dev_name(&dev_dax->dev)) != 0)
+		return false;
+	last = &dev_dax->ranges[dev_dax->nr_range - 1];
+	if (last->range.start != res->start || last->range.end != res->end)
+		return false;
+	for (i = 0; i < dev_dax->nr_range - 1; i++) {
+		struct dev_dax_range *dax_range = &dev_dax->ranges[i];
+
+		if (dax_range->pgoff > last->pgoff)
+			return false;
+	}
+
+	return true;
+}
+
+static ssize_t dev_dax_resize(struct dax_region *dax_region,
+		struct dev_dax *dev_dax, resource_size_t size)
+{
+	resource_size_t avail = dax_region_avail_size(dax_region), to_alloc;
+	resource_size_t dev_size = dev_dax_size(dev_dax);
+	struct resource *region_res = &dax_region->res;
+	struct device *dev = &dev_dax->dev;
+	struct resource *res, *first;
+	resource_size_t alloc = 0;
+	int rc;
+
+	if (dev->driver)
+		return -EBUSY;
+	if (size == dev_size)
+		return 0;
+	if (size > dev_size && size - dev_size > avail)
+		return -ENOSPC;
+	if (size < dev_size)
+		return dev_dax_shrink(dev_dax, size);
+
+	to_alloc = size - dev_size;
+	if (dev_WARN_ONCE(dev, !alloc_is_aligned(dev_dax, to_alloc),
+			"resize of %pa misaligned\n", &to_alloc))
+		return -ENXIO;
+
+	/*
+	 * Expand the device into the unused portion of the region. This
+	 * may involve adjusting the end of an existing resource, or
+	 * allocating a new resource.
+	 */
+retry:
+	first = region_res->child;
+	if (!first)
+		return alloc_dev_dax_range(dev_dax, dax_region->res.start, to_alloc);
+
+	rc = -ENOSPC;
+	for (res = first; res; res = res->sibling) {
+		struct resource *next = res->sibling;
+
+		/* space at the beginning of the region */
+		if (res == first && res->start > dax_region->res.start) {
+			alloc = min(res->start - dax_region->res.start, to_alloc);
+			rc = alloc_dev_dax_range(dev_dax, dax_region->res.start, alloc);
+			break;
+		}
+
+		alloc = 0;
+		/* space between allocations */
+		if (next && next->start > res->end + 1)
+			alloc = min(next->start - (res->end + 1), to_alloc);
+
+		/* space at the end of the region */
+		if (!alloc && !next && res->end < region_res->end)
+			alloc = min(region_res->end - res->end, to_alloc);
+
+		if (!alloc)
+			continue;
+
+		if (adjust_ok(dev_dax, res)) {
+			rc = adjust_dev_dax_range(dev_dax, res, resource_size(res) + alloc);
+			break;
+		}
+		rc = alloc_dev_dax_range(dev_dax, res->end + 1, alloc);
+		break;
+	}
+	if (rc)
+		return rc;
+	to_alloc -= alloc;
+	if (to_alloc)
+		goto retry;
+	return 0;
+}
+
+static ssize_t size_store(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t len)
+{
+	ssize_t rc;
+	unsigned long long val;
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	struct dax_region *dax_region = dev_dax->region;
+
+	rc = kstrtoull(buf, 0, &val);
+	if (rc)
+		return rc;
+
+	if (!alloc_is_aligned(dev_dax, val)) {
+		dev_dbg(dev, "%s: size: %lld misaligned\n", __func__, val);
+		return -EINVAL;
+	}
+
+	device_lock(dax_region->dev);
+	if (!dax_region->dev->driver) {
+		device_unlock(dax_region->dev);
+		return -ENXIO;
+	}
+	device_lock(dev);
+	rc = dev_dax_resize(dax_region, dev_dax, val);
+	device_unlock(dev);
+	device_unlock(dax_region->dev);
+
+	return rc == 0 ? len : rc;
+}
+static DEVICE_ATTR_RW(size);
+
+static ssize_t range_parse(const char *opt, size_t len, struct range *range)
+{
+	unsigned long long addr = 0;
+	char *start, *end, *str;
+	ssize_t rc = -EINVAL;
+
+	str = kstrdup(opt, GFP_KERNEL);
+	if (!str)
+		return rc;
+
+	end = str;
+	start = strsep(&end, "-");
+	if (!start || !end)
+		goto err;
+
+	rc = kstrtoull(start, 16, &addr);
+	if (rc)
+		goto err;
+	range->start = addr;
+
+	rc = kstrtoull(end, 16, &addr);
+	if (rc)
+		goto err;
+	range->end = addr;
+
+err:
+	kfree(str);
+	return rc;
+}
+
+static ssize_t mapping_store(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t len)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	struct dax_region *dax_region = dev_dax->region;
+	size_t to_alloc;
+	struct range r;
+	ssize_t rc;
+
+	rc = range_parse(buf, len, &r);
+	if (rc)
+		return rc;
+
+	rc = -ENXIO;
+	device_lock(dax_region->dev);
+	if (!dax_region->dev->driver) {
+		device_unlock(dax_region->dev);
+		return rc;
+	}
+	device_lock(dev);
+
+	to_alloc = range_len(&r);
+	if (alloc_is_aligned(dev_dax, to_alloc))
+		rc = alloc_dev_dax_range(dev_dax, r.start, to_alloc);
+	device_unlock(dev);
+	device_unlock(dax_region->dev);
+
+	return rc == 0 ? len : rc;
+}
+static DEVICE_ATTR_WO(mapping);
+
+static ssize_t align_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+
+	return sprintf(buf, "%d\n", dev_dax->align);
+}
+
+static ssize_t dev_dax_validate_align(struct dev_dax *dev_dax)
+{
+	struct device *dev = &dev_dax->dev;
+	int i;
+
+	for (i = 0; i < dev_dax->nr_range; i++) {
+		size_t len = range_len(&dev_dax->ranges[i].range);
+
+		if (!alloc_is_aligned(dev_dax, len)) {
+			dev_dbg(dev, "%s: align %u invalid for range %d\n",
+				__func__, dev_dax->align, i);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+static ssize_t align_store(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t len)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	struct dax_region *dax_region = dev_dax->region;
+	unsigned long val, align_save;
+	ssize_t rc;
+
+	rc = kstrtoul(buf, 0, &val);
+	if (rc)
+		return -ENXIO;
+
+	if (!dax_align_valid(val))
+		return -EINVAL;
+
+	device_lock(dax_region->dev);
+	if (!dax_region->dev->driver) {
+		device_unlock(dax_region->dev);
+		return -ENXIO;
+	}
+
+	device_lock(dev);
+	if (dev->driver) {
+		rc = -EBUSY;
+		goto out_unlock;
+	}
+
+	align_save = dev_dax->align;
+	dev_dax->align = val;
+	rc = dev_dax_validate_align(dev_dax);
+	if (rc)
+		dev_dax->align = align_save;
+out_unlock:
+	device_unlock(dev);
+	device_unlock(dax_region->dev);
+	return rc == 0 ? len : rc;
+}
+static DEVICE_ATTR_RW(align);
+
+static int dev_dax_target_node(struct dev_dax *dev_dax)
+{
+	struct dax_region *dax_region = dev_dax->region;
+
+	return dax_region->target_node;
+}
+
+static ssize_t target_node_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+
+	return sprintf(buf, "%d\n", dev_dax_target_node(dev_dax));
+}
+static DEVICE_ATTR_RO(target_node);
+
+static ssize_t resource_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	struct dax_region *dax_region = dev_dax->region;
+	unsigned long long start;
+
+	if (dev_dax->nr_range < 1)
+		start = dax_region->res.start;
+	else
+		start = dev_dax->ranges[0].range.start;
+
+	return sprintf(buf, "%#llx\n", start);
+}
+static DEVICE_ATTR(resource, 0400, resource_show, NULL);
+
+static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	/*
+	 * We only ever expect to handle device-dax instances, i.e. the
+	 * @type argument to MODULE_ALIAS_DAX_DEVICE() is always zero
+	 */
+	return sprintf(buf, DAX_DEVICE_MODALIAS_FMT "\n", 0);
+}
+static DEVICE_ATTR_RO(modalias);
+
+static ssize_t numa_node_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", dev_to_node(dev));
+}
+static DEVICE_ATTR_RO(numa_node);
+
+static umode_t dev_dax_visible(struct kobject *kobj, struct attribute *a, int n)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	struct dax_region *dax_region = dev_dax->region;
+
+	if (a == &dev_attr_target_node.attr && dev_dax_target_node(dev_dax) < 0)
+		return 0;
+	if (a == &dev_attr_numa_node.attr && !IS_ENABLED(CONFIG_NUMA))
+		return 0;
+	if (a == &dev_attr_mapping.attr && is_static(dax_region))
+		return 0;
+	if ((a == &dev_attr_align.attr ||
+	     a == &dev_attr_size.attr) && is_static(dax_region))
+		return 0444;
+	return a->mode;
+}
+
+static struct attribute *dev_dax_attributes[] = {
+	&dev_attr_modalias.attr,
+	&dev_attr_size.attr,
+	&dev_attr_mapping.attr,
+	&dev_attr_target_node.attr,
+	&dev_attr_align.attr,
+	&dev_attr_resource.attr,
+	&dev_attr_numa_node.attr,
+	NULL,
+};
+
+static const struct attribute_group dev_dax_attribute_group = {
+	.attrs = dev_dax_attributes,
+	.is_visible = dev_dax_visible,
+};
+
+static const struct attribute_group *dax_attribute_groups[] = {
+	&dev_dax_attribute_group,
+	NULL,
+};
+
+static void dev_dax_release(struct device *dev)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	struct dax_device *dax_dev = dev_dax->dax_dev;
+
+	put_dax(dax_dev);
+	free_dev_dax_id(dev_dax);
+	kfree(dev_dax->pgmap);
+	kfree(dev_dax);
+}
+
+static const struct device_type dev_dax_type = {
+	.release = dev_dax_release,
+	.groups = dax_attribute_groups,
+};
+
+struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
+{
+	struct dax_region *dax_region = data->dax_region;
+	struct device *parent = dax_region->dev;
+	struct dax_device *dax_dev;
+	struct dev_dax *dev_dax;
+	struct inode *inode;
+	struct device *dev;
+	int rc;
+
+	dev_dax = kzalloc(sizeof(*dev_dax), GFP_KERNEL);
+	if (!dev_dax)
+		return ERR_PTR(-ENOMEM);
+
+	dev_dax->region = dax_region;
+	if (is_static(dax_region)) {
+		if (dev_WARN_ONCE(parent, data->id < 0,
+				"dynamic id specified to static region\n")) {
+			rc = -EINVAL;
+			goto err_id;
+		}
+
+		dev_dax->id = data->id;
+	} else {
+		if (dev_WARN_ONCE(parent, data->id >= 0,
+				"static id specified to dynamic region\n")) {
+			rc = -EINVAL;
+			goto err_id;
+		}
+
+		rc = alloc_dev_dax_id(dev_dax);
+		if (rc < 0)
+			goto err_id;
+	}
+
+	dev = &dev_dax->dev;
+	device_initialize(dev);
+	dev_set_name(dev, "dax%d.%d", dax_region->id, dev_dax->id);
+
+	rc = alloc_dev_dax_range(dev_dax, dax_region->res.start, data->size);
+	if (rc)
+		goto err_range;
+
+	if (data->pgmap) {
+		dev_WARN_ONCE(parent, !is_static(dax_region),
+			"custom dev_pagemap requires a static dax_region\n");
+
+		dev_dax->pgmap = kmemdup(data->pgmap,
+				sizeof(struct dev_pagemap), GFP_KERNEL);
+		if (!dev_dax->pgmap) {
+			rc = -ENOMEM;
+			goto err_pgmap;
+		}
+	}
+
+	/*
+	 * No dax_operations since there is no access to this device outside of
+	 * mmap of the resulting character device.
+	 */
+	dax_dev = alloc_dax(dev_dax, NULL);
+	if (IS_ERR(dax_dev)) {
+		rc = PTR_ERR(dax_dev);
+		goto err_alloc_dax;
+	}
+	set_dax_synchronous(dax_dev);
+	set_dax_nocache(dax_dev);
+	set_dax_nomc(dax_dev);
+
+	/* a device_dax instance is dead while the driver is not attached */
+	kill_dax(dax_dev);
+
+	dev_dax->dax_dev = dax_dev;
+	dev_dax->target_node = dax_region->target_node;
+	dev_dax->align = dax_region->align;
+	ida_init(&dev_dax->ida);
+
+	inode = dax_inode(dax_dev);
+	dev->devt = inode->i_rdev;
+	dev->bus = &dax_bus_type;
+	dev->parent = parent;
+	dev->type = &dev_dax_type;
+
+	rc = device_add(dev);
+	if (rc) {
+		kill_dev_dax(dev_dax);
+		put_device(dev);
+		return ERR_PTR(rc);
+	}
+
+	rc = devm_add_action_or_reset(dax_region->dev, unregister_dev_dax, dev);
+	if (rc)
+		return ERR_PTR(rc);
+
+	/* register mapping device for the initial allocation range */
+	if (dev_dax->nr_range && range_len(&dev_dax->ranges[0].range)) {
+		rc = devm_register_dax_mapping(dev_dax, 0);
+		if (rc)
+			return ERR_PTR(rc);
+	}
+
+	return dev_dax;
+
+err_alloc_dax:
+	kfree(dev_dax->pgmap);
+err_pgmap:
+	free_dev_dax_ranges(dev_dax);
+err_range:
+	free_dev_dax_id(dev_dax);
+err_id:
+	kfree(dev_dax);
+
+	return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_GPL(devm_create_dev_dax);
+
+static int match_always_count;
+
+int __dax_driver_register(struct dax_device_driver *dax_drv,
+		struct module *module, const char *mod_name)
+{
+	struct device_driver *drv = &dax_drv->drv;
+	int rc = 0;
+
+	/*
+	 * dax_bus_probe() calls dax_drv->probe() unconditionally.
+	 * So better be safe than sorry and ensure it is provided.
+	 */
+	if (!dax_drv->probe)
+		return -EINVAL;
+
+	INIT_LIST_HEAD(&dax_drv->ids);
+	drv->owner = module;
+	drv->name = mod_name;
+	drv->mod_name = mod_name;
+	drv->bus = &dax_bus_type;
+
+	/* there can only be one default driver */
+	mutex_lock(&dax_bus_lock);
+	match_always_count += dax_drv->match_always;
+	if (match_always_count > 1) {
+		match_always_count--;
+		WARN_ON(1);
+		rc = -EINVAL;
+	}
+	mutex_unlock(&dax_bus_lock);
+	if (rc)
+		return rc;
+
+	rc = driver_register(drv);
+	if (rc && dax_drv->match_always) {
+		mutex_lock(&dax_bus_lock);
+		match_always_count -= dax_drv->match_always;
+		mutex_unlock(&dax_bus_lock);
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(__dax_driver_register);
+
+void dax_driver_unregister(struct dax_device_driver *dax_drv)
+{
+	struct device_driver *drv = &dax_drv->drv;
+	struct dax_id *dax_id, *_id;
+
+	mutex_lock(&dax_bus_lock);
+	match_always_count -= dax_drv->match_always;
+	list_for_each_entry_safe(dax_id, _id, &dax_drv->ids, list) {
+		list_del(&dax_id->list);
+		kfree(dax_id);
+	}
+	mutex_unlock(&dax_bus_lock);
+	driver_unregister(drv);
+}
+EXPORT_SYMBOL_GPL(dax_driver_unregister);
+
+int __init dax_bus_init(void)
+{
+	return bus_register(&dax_bus_type);
+}
+
+void __exit dax_bus_exit(void)
+{
+	bus_unregister(&dax_bus_type);
+}
diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
new file mode 100644
index 000000000..fbb940293
--- /dev/null
+++ b/drivers/dax/bus.h
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016 - 2018 Intel Corporation. All rights reserved. */
+#ifndef __DAX_BUS_H__
+#define __DAX_BUS_H__
+#include <linux/device.h>
+#include <linux/range.h>
+
+struct dev_dax;
+struct resource;
+struct dax_device;
+struct dax_region;
+void dax_region_put(struct dax_region *dax_region);
+
+#define IORESOURCE_DAX_STATIC (1UL << 0)
+struct dax_region *alloc_dax_region(struct device *parent, int region_id,
+		struct range *range, int target_node, unsigned int align,
+		unsigned long flags);
+
+struct dev_dax_data {
+	struct dax_region *dax_region;
+	struct dev_pagemap *pgmap;
+	resource_size_t size;
+	int id;
+};
+
+struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data);
+
+struct dax_device_driver {
+	struct device_driver drv;
+	struct list_head ids;
+	int match_always;
+	int (*probe)(struct dev_dax *dev);
+	void (*remove)(struct dev_dax *dev);
+};
+
+int __dax_driver_register(struct dax_device_driver *dax_drv,
+		struct module *module, const char *mod_name);
+#define dax_driver_register(driver) \
+	__dax_driver_register(driver, THIS_MODULE, KBUILD_MODNAME)
+void dax_driver_unregister(struct dax_device_driver *dax_drv);
+void kill_dev_dax(struct dev_dax *dev_dax);
+bool static_dev_dax(struct dev_dax *dev_dax);
+
+/*
+ * While run_dax() is potentially a generic operation that could be
+ * defined in include/linux/dax.h we don't want to grow any users
+ * outside of drivers/dax/
+ */
+void run_dax(struct dax_device *dax_dev);
+
+#define MODULE_ALIAS_DAX_DEVICE(type) \
+	MODULE_ALIAS("dax:t" __stringify(type) "*")
+#define DAX_DEVICE_MODALIAS_FMT "dax:t%d"
+
+#endif /* __DAX_BUS_H__ */
diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
new file mode 100644
index 000000000..afcada6fd
--- /dev/null
+++ b/drivers/dax/dax-private.h
@@ -0,0 +1,110 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright(c) 2016 Intel Corporation. All rights reserved.
+ */
+#ifndef __DAX_PRIVATE_H__
+#define __DAX_PRIVATE_H__
+
+#include <linux/device.h>
+#include <linux/cdev.h>
+#include <linux/idr.h>
+
+/* private routines between core files */
+struct dax_device;
+struct dax_device *inode_dax(struct inode *inode);
+struct inode *dax_inode(struct dax_device *dax_dev);
+int dax_bus_init(void);
+void dax_bus_exit(void);
+
+/**
+ * struct dax_region - mapping infrastructure for dax devices
+ * @id: kernel-wide unique region for a memory range
+ * @target_node: effective numa node if this memory range is onlined
+ * @kref: to pin while other agents have a need to do lookups
+ * @dev: parent device backing this region
+ * @align: allocation and mapping alignment for child dax devices
+ * @ida: instance id allocator
+ * @res: resource tree to track instance allocations
+ * @seed: allow userspace to find the first unbound seed device
+ * @youngest: allow userspace to find the most recently created device
+ */
+struct dax_region {
+	int id;
+	int target_node;
+	struct kref kref;
+	struct device *dev;
+	unsigned int align;
+	struct ida ida;
+	struct resource res;
+	struct device *seed;
+	struct device *youngest;
+};
+
+struct dax_mapping {
+	struct device dev;
+	int range_id;
+	int id;
+};
+
+/**
+ * struct dev_dax - instance data for a subdivision of a dax region, and
+ * data while the device is activated in the driver.
+ * @region - parent region
+ * @dax_dev - core dax functionality
+ * @target_node: effective numa node if dev_dax memory range is onlined
+ * @dyn_id: is this a dynamic or statically created instance
+ * @id: ida allocated id when the dax_region is not static
+ * @ida: mapping id allocator
+ * @dev - device core
+ * @pgmap - pgmap for memmap setup / lifetime (driver owned)
+ * @nr_range: size of @ranges
+ * @ranges: resource-span + pgoff tuples for the instance
+ */
+struct dev_dax {
+	struct dax_region *region;
+	struct dax_device *dax_dev;
+	unsigned int align;
+	int target_node;
+	bool dyn_id;
+	int id;
+	struct ida ida;
+	struct device dev;
+	struct dev_pagemap *pgmap;
+	int nr_range;
+	struct dev_dax_range {
+		unsigned long pgoff;
+		struct range range;
+		struct dax_mapping *mapping;
+	} *ranges;
+};
+
+static inline struct dev_dax *to_dev_dax(struct device *dev)
+{
+	return container_of(dev, struct dev_dax, dev);
+}
+
+static inline struct dax_mapping *to_dax_mapping(struct device *dev)
+{
+	return container_of(dev, struct dax_mapping, dev);
+}
+
+phys_addr_t dax_pgoff_to_phys(struct dev_dax *dev_dax, pgoff_t pgoff, unsigned long size);
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static inline bool dax_align_valid(unsigned long align)
+{
+	if (align == PUD_SIZE && IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD))
+		return true;
+	if (align == PMD_SIZE && has_transparent_hugepage())
+		return true;
+	if (align == PAGE_SIZE)
+		return true;
+	return false;
+}
+#else
+static inline bool dax_align_valid(unsigned long align)
+{
+	return align == PAGE_SIZE;
+}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#endif
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
new file mode 100644
index 000000000..5494d745c
--- /dev/null
+++ b/drivers/dax/device.c
@@ -0,0 +1,496 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016-2018 Intel Corporation. All rights reserved. */
+#include <linux/memremap.h>
+#include <linux/pagemap.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/pfn_t.h>
+#include <linux/cdev.h>
+#include <linux/slab.h>
+#include <linux/dax.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include "dax-private.h"
+#include "bus.h"
+
+static int check_vma(struct dev_dax *dev_dax, struct vm_area_struct *vma,
+		const char *func)
+{
+	struct device *dev = &dev_dax->dev;
+	unsigned long mask;
+
+	if (!dax_alive(dev_dax->dax_dev))
+		return -ENXIO;
+
+	/* prevent private mappings from being established */
+	if ((vma->vm_flags & VM_MAYSHARE) != VM_MAYSHARE) {
+		dev_info_ratelimited(dev,
+				"%s: %s: fail, attempted private mapping\n",
+				current->comm, func);
+		return -EINVAL;
+	}
+
+	mask = dev_dax->align - 1;
+	if (vma->vm_start & mask || vma->vm_end & mask) {
+		dev_info_ratelimited(dev,
+				"%s: %s: fail, unaligned vma (%#lx - %#lx, %#lx)\n",
+				current->comm, func, vma->vm_start, vma->vm_end,
+				mask);
+		return -EINVAL;
+	}
+
+	if (!vma_is_dax(vma)) {
+		dev_info_ratelimited(dev,
+				"%s: %s: fail, vma is not DAX capable\n",
+				current->comm, func);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* see "strong" declaration in tools/testing/nvdimm/dax-dev.c */
+__weak phys_addr_t dax_pgoff_to_phys(struct dev_dax *dev_dax, pgoff_t pgoff,
+		unsigned long size)
+{
+	int i;
+
+	for (i = 0; i < dev_dax->nr_range; i++) {
+		struct dev_dax_range *dax_range = &dev_dax->ranges[i];
+		struct range *range = &dax_range->range;
+		unsigned long long pgoff_end;
+		phys_addr_t phys;
+
+		pgoff_end = dax_range->pgoff + PHYS_PFN(range_len(range)) - 1;
+		if (pgoff < dax_range->pgoff || pgoff > pgoff_end)
+			continue;
+		phys = PFN_PHYS(pgoff - dax_range->pgoff) + range->start;
+		if (phys + size - 1 <= range->end)
+			return phys;
+		break;
+	}
+	return -1;
+}
+
+static void dax_set_mapping(struct vm_fault *vmf, pfn_t pfn,
+			      unsigned long fault_size)
+{
+	unsigned long i, nr_pages = fault_size / PAGE_SIZE;
+	struct file *filp = vmf->vma->vm_file;
+	struct dev_dax *dev_dax = filp->private_data;
+	pgoff_t pgoff;
+
+	/* mapping is only set on the head */
+	if (dev_dax->pgmap->vmemmap_shift)
+		nr_pages = 1;
+
+	pgoff = linear_page_index(vmf->vma,
+			ALIGN(vmf->address, fault_size));
+
+	for (i = 0; i < nr_pages; i++) {
+		struct page *page = pfn_to_page(pfn_t_to_pfn(pfn) + i);
+
+		page = compound_head(page);
+		if (page->mapping)
+			continue;
+
+		page->mapping = filp->f_mapping;
+		page->index = pgoff + i;
+	}
+}
+
+static vm_fault_t __dev_dax_pte_fault(struct dev_dax *dev_dax,
+				struct vm_fault *vmf)
+{
+	struct device *dev = &dev_dax->dev;
+	phys_addr_t phys;
+	pfn_t pfn;
+	unsigned int fault_size = PAGE_SIZE;
+
+	if (check_vma(dev_dax, vmf->vma, __func__))
+		return VM_FAULT_SIGBUS;
+
+	if (dev_dax->align > PAGE_SIZE) {
+		dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
+			dev_dax->align, fault_size);
+		return VM_FAULT_SIGBUS;
+	}
+
+	if (fault_size != dev_dax->align)
+		return VM_FAULT_SIGBUS;
+
+	phys = dax_pgoff_to_phys(dev_dax, vmf->pgoff, PAGE_SIZE);
+	if (phys == -1) {
+		dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", vmf->pgoff);
+		return VM_FAULT_SIGBUS;
+	}
+
+	pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);
+
+	dax_set_mapping(vmf, pfn, fault_size);
+
+	return vmf_insert_mixed(vmf->vma, vmf->address, pfn);
+}
+
+static vm_fault_t __dev_dax_pmd_fault(struct dev_dax *dev_dax,
+				struct vm_fault *vmf)
+{
+	unsigned long pmd_addr = vmf->address & PMD_MASK;
+	struct device *dev = &dev_dax->dev;
+	phys_addr_t phys;
+	pgoff_t pgoff;
+	pfn_t pfn;
+	unsigned int fault_size = PMD_SIZE;
+
+	if (check_vma(dev_dax, vmf->vma, __func__))
+		return VM_FAULT_SIGBUS;
+
+	if (dev_dax->align > PMD_SIZE) {
+		dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
+			dev_dax->align, fault_size);
+		return VM_FAULT_SIGBUS;
+	}
+
+	if (fault_size < dev_dax->align)
+		return VM_FAULT_SIGBUS;
+	else if (fault_size > dev_dax->align)
+		return VM_FAULT_FALLBACK;
+
+	/* if we are outside of the VMA */
+	if (pmd_addr < vmf->vma->vm_start ||
+			(pmd_addr + PMD_SIZE) > vmf->vma->vm_end)
+		return VM_FAULT_SIGBUS;
+
+	pgoff = linear_page_index(vmf->vma, pmd_addr);
+	phys = dax_pgoff_to_phys(dev_dax, pgoff, PMD_SIZE);
+	if (phys == -1) {
+		dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", pgoff);
+		return VM_FAULT_SIGBUS;
+	}
+
+	pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);
+
+	dax_set_mapping(vmf, pfn, fault_size);
+
+	return vmf_insert_pfn_pmd(vmf, pfn, vmf->flags & FAULT_FLAG_WRITE);
+}
+
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+static vm_fault_t __dev_dax_pud_fault(struct dev_dax *dev_dax,
+				struct vm_fault *vmf)
+{
+	unsigned long pud_addr = vmf->address & PUD_MASK;
+	struct device *dev = &dev_dax->dev;
+	phys_addr_t phys;
+	pgoff_t pgoff;
+	pfn_t pfn;
+	unsigned int fault_size = PUD_SIZE;
+
+
+	if (check_vma(dev_dax, vmf->vma, __func__))
+		return VM_FAULT_SIGBUS;
+
+	if (dev_dax->align > PUD_SIZE) {
+		dev_dbg(dev, "alignment (%#x) > fault size (%#x)\n",
+			dev_dax->align, fault_size);
+		return VM_FAULT_SIGBUS;
+	}
+
+	if (fault_size < dev_dax->align)
+		return VM_FAULT_SIGBUS;
+	else if (fault_size > dev_dax->align)
+		return VM_FAULT_FALLBACK;
+
+	/* if we are outside of the VMA */
+	if (pud_addr < vmf->vma->vm_start ||
+			(pud_addr + PUD_SIZE) > vmf->vma->vm_end)
+		return VM_FAULT_SIGBUS;
+
+	pgoff = linear_page_index(vmf->vma, pud_addr);
+	phys = dax_pgoff_to_phys(dev_dax, pgoff, PUD_SIZE);
+	if (phys == -1) {
+		dev_dbg(dev, "pgoff_to_phys(%#lx) failed\n", pgoff);
+		return VM_FAULT_SIGBUS;
+	}
+
+	pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);
+
+	dax_set_mapping(vmf, pfn, fault_size);
+
+	return vmf_insert_pfn_pud(vmf, pfn, vmf->flags & FAULT_FLAG_WRITE);
+}
+#else
+static vm_fault_t __dev_dax_pud_fault(struct dev_dax *dev_dax,
+				struct vm_fault *vmf)
+{
+	return VM_FAULT_FALLBACK;
+}
+#endif /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+
+static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
+		enum page_entry_size pe_size)
+{
+	struct file *filp = vmf->vma->vm_file;
+	vm_fault_t rc = VM_FAULT_SIGBUS;
+	int id;
+	struct dev_dax *dev_dax = filp->private_data;
+
+	dev_dbg(&dev_dax->dev, "%s: %s (%#lx - %#lx) size = %d\n", current->comm,
+			(vmf->flags & FAULT_FLAG_WRITE) ? "write" : "read",
+			vmf->vma->vm_start, vmf->vma->vm_end, pe_size);
+
+	id = dax_read_lock();
+	switch (pe_size) {
+	case PE_SIZE_PTE:
+		rc = __dev_dax_pte_fault(dev_dax, vmf);
+		break;
+	case PE_SIZE_PMD:
+		rc = __dev_dax_pmd_fault(dev_dax, vmf);
+		break;
+	case PE_SIZE_PUD:
+		rc = __dev_dax_pud_fault(dev_dax, vmf);
+		break;
+	default:
+		rc = VM_FAULT_SIGBUS;
+	}
+
+	dax_read_unlock(id);
+
+	return rc;
+}
+
+static vm_fault_t dev_dax_fault(struct vm_fault *vmf)
+{
+	return dev_dax_huge_fault(vmf, PE_SIZE_PTE);
+}
+
+static int dev_dax_may_split(struct vm_area_struct *vma, unsigned long addr)
+{
+	struct file *filp = vma->vm_file;
+	struct dev_dax *dev_dax = filp->private_data;
+
+	if (!IS_ALIGNED(addr, dev_dax->align))
+		return -EINVAL;
+	return 0;
+}
+
+static unsigned long dev_dax_pagesize(struct vm_area_struct *vma)
+{
+	struct file *filp = vma->vm_file;
+	struct dev_dax *dev_dax = filp->private_data;
+
+	return dev_dax->align;
+}
+
+static const struct vm_operations_struct dax_vm_ops = {
+	.fault = dev_dax_fault,
+	.huge_fault = dev_dax_huge_fault,
+	.may_split = dev_dax_may_split,
+	.pagesize = dev_dax_pagesize,
+};
+
+static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct dev_dax *dev_dax = filp->private_data;
+	int rc, id;
+
+	dev_dbg(&dev_dax->dev, "trace\n");
+
+	/*
+	 * We lock to check dax_dev liveness and will re-check at
+	 * fault time.
+	 */
+	id = dax_read_lock();
+	rc = check_vma(dev_dax, vma, __func__);
+	dax_read_unlock(id);
+	if (rc)
+		return rc;
+
+	vma->vm_ops = &dax_vm_ops;
+	vma->vm_flags |= VM_HUGEPAGE;
+	return 0;
+}
+
+/* return an unmapped area aligned to the dax region specified alignment */
+static unsigned long dax_get_unmapped_area(struct file *filp,
+		unsigned long addr, unsigned long len, unsigned long pgoff,
+		unsigned long flags)
+{
+	unsigned long off, off_end, off_align, len_align, addr_align, align;
+	struct dev_dax *dev_dax = filp ? filp->private_data : NULL;
+
+	if (!dev_dax || addr)
+		goto out;
+
+	align = dev_dax->align;
+	off = pgoff << PAGE_SHIFT;
+	off_end = off + len;
+	off_align = round_up(off, align);
+
+	if ((off_end <= off_align) || ((off_end - off_align) < align))
+		goto out;
+
+	len_align = len + align;
+	if ((off + len_align) < off)
+		goto out;
+
+	addr_align = current->mm->get_unmapped_area(filp, addr, len_align,
+			pgoff, flags);
+	if (!IS_ERR_VALUE(addr_align)) {
+		addr_align += (off - addr_align) & (align - 1);
+		return addr_align;
+	}
+ out:
+	return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
+}
+
+static const struct address_space_operations dev_dax_aops = {
+	.dirty_folio	= noop_dirty_folio,
+};
+
+static int dax_open(struct inode *inode, struct file *filp)
+{
+	struct dax_device *dax_dev = inode_dax(inode);
+	struct inode *__dax_inode = dax_inode(dax_dev);
+	struct dev_dax *dev_dax = dax_get_private(dax_dev);
+
+	dev_dbg(&dev_dax->dev, "trace\n");
+	inode->i_mapping = __dax_inode->i_mapping;
+	inode->i_mapping->host = __dax_inode;
+	inode->i_mapping->a_ops = &dev_dax_aops;
+	filp->f_mapping = inode->i_mapping;
+	filp->f_wb_err = filemap_sample_wb_err(filp->f_mapping);
+	filp->f_sb_err = file_sample_sb_err(filp);
+	filp->private_data = dev_dax;
+	inode->i_flags = S_DAX;
+
+	return 0;
+}
+
+static int dax_release(struct inode *inode, struct file *filp)
+{
+	struct dev_dax *dev_dax = filp->private_data;
+
+	dev_dbg(&dev_dax->dev, "trace\n");
+	return 0;
+}
+
+static const struct file_operations dax_fops = {
+	.llseek = noop_llseek,
+	.owner = THIS_MODULE,
+	.open = dax_open,
+	.release = dax_release,
+	.get_unmapped_area = dax_get_unmapped_area,
+	.mmap = dax_mmap,
+	.mmap_supported_flags = MAP_SYNC,
+};
+
+static void dev_dax_cdev_del(void *cdev)
+{
+	cdev_del(cdev);
+}
+
+static void dev_dax_kill(void *dev_dax)
+{
+	kill_dev_dax(dev_dax);
+}
+
+int dev_dax_probe(struct dev_dax *dev_dax)
+{
+	struct dax_device *dax_dev = dev_dax->dax_dev;
+	struct device *dev = &dev_dax->dev;
+	struct dev_pagemap *pgmap;
+	struct inode *inode;
+	struct cdev *cdev;
+	void *addr;
+	int rc, i;
+
+	if (static_dev_dax(dev_dax))  {
+		if (dev_dax->nr_range > 1) {
+			dev_warn(dev,
+				"static pgmap / multi-range device conflict\n");
+			return -EINVAL;
+		}
+
+		pgmap = dev_dax->pgmap;
+	} else {
+		if (dev_dax->pgmap) {
+			dev_warn(dev,
+				 "dynamic-dax with pre-populated page map\n");
+			return -EINVAL;
+		}
+
+		pgmap = devm_kzalloc(dev,
+                       struct_size(pgmap, ranges, dev_dax->nr_range - 1),
+                       GFP_KERNEL);
+		if (!pgmap)
+			return -ENOMEM;
+
+		pgmap->nr_range = dev_dax->nr_range;
+		dev_dax->pgmap = pgmap;
+
+		for (i = 0; i < dev_dax->nr_range; i++) {
+			struct range *range = &dev_dax->ranges[i].range;
+			pgmap->ranges[i] = *range;
+		}
+	}
+
+	for (i = 0; i < dev_dax->nr_range; i++) {
+		struct range *range = &dev_dax->ranges[i].range;
+
+		if (!devm_request_mem_region(dev, range->start,
+					range_len(range), dev_name(dev))) {
+			dev_warn(dev, "mapping%d: %#llx-%#llx could not reserve range\n",
+					i, range->start, range->end);
+			return -EBUSY;
+		}
+	}
+
+	pgmap->type = MEMORY_DEVICE_GENERIC;
+	if (dev_dax->align > PAGE_SIZE)
+		pgmap->vmemmap_shift =
+			order_base_2(dev_dax->align >> PAGE_SHIFT);
+	addr = devm_memremap_pages(dev, pgmap);
+	if (IS_ERR(addr))
+		return PTR_ERR(addr);
+
+	inode = dax_inode(dax_dev);
+	cdev = inode->i_cdev;
+	cdev_init(cdev, &dax_fops);
+	cdev->owner = dev->driver->owner;
+	cdev_set_parent(cdev, &dev->kobj);
+	rc = cdev_add(cdev, dev->devt, 1);
+	if (rc)
+		return rc;
+
+	rc = devm_add_action_or_reset(dev, dev_dax_cdev_del, cdev);
+	if (rc)
+		return rc;
+
+	run_dax(dax_dev);
+	return devm_add_action_or_reset(dev, dev_dax_kill, dev_dax);
+}
+EXPORT_SYMBOL_GPL(dev_dax_probe);
+
+static struct dax_device_driver device_dax_driver = {
+	.probe = dev_dax_probe,
+	/* all probe actions are unwound by devm, so .remove isn't necessary */
+	.match_always = 1,
+};
+
+static int __init dax_init(void)
+{
+	return dax_driver_register(&device_dax_driver);
+}
+
+static void __exit dax_exit(void)
+{
+	dax_driver_unregister(&device_dax_driver);
+}
+
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL v2");
+module_init(dax_init);
+module_exit(dax_exit);
+MODULE_ALIAS_DAX_DEVICE(0);
diff --git a/drivers/dax/hmem/Makefile b/drivers/dax/hmem/Makefile
new file mode 100644
index 000000000..57377b4c3
--- /dev/null
+++ b/drivers/dax/hmem/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_DEV_DAX_HMEM) += dax_hmem.o
+obj-$(CONFIG_DEV_DAX_HMEM_DEVICES) += device_hmem.o
+
+device_hmem-y := device.o
+dax_hmem-y := hmem.o
diff --git a/drivers/dax/hmem/device.c b/drivers/dax/hmem/device.c
new file mode 100644
index 000000000..903325aac
--- /dev/null
+++ b/drivers/dax/hmem/device.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/platform_device.h>
+#include <linux/memregion.h>
+#include <linux/module.h>
+#include <linux/dax.h>
+#include <linux/mm.h>
+
+static bool nohmem;
+module_param_named(disable, nohmem, bool, 0444);
+
+static struct resource hmem_active = {
+	.name = "HMEM devices",
+	.start = 0,
+	.end = -1,
+	.flags = IORESOURCE_MEM,
+};
+
+void hmem_register_device(int target_nid, struct resource *r)
+{
+	/* define a clean / non-busy resource for the platform device */
+	struct resource res = {
+		.start = r->start,
+		.end = r->end,
+		.flags = IORESOURCE_MEM,
+		.desc = IORES_DESC_SOFT_RESERVED,
+	};
+	struct platform_device *pdev;
+	struct memregion_info info;
+	int rc, id;
+
+	if (nohmem)
+		return;
+
+	rc = region_intersects(res.start, resource_size(&res), IORESOURCE_MEM,
+			IORES_DESC_SOFT_RESERVED);
+	if (rc != REGION_INTERSECTS)
+		return;
+
+	id = memregion_alloc(GFP_KERNEL);
+	if (id < 0) {
+		pr_err("memregion allocation failure for %pr\n", &res);
+		return;
+	}
+
+	pdev = platform_device_alloc("hmem", id);
+	if (!pdev) {
+		pr_err("hmem device allocation failure for %pr\n", &res);
+		goto out_pdev;
+	}
+
+	if (!__request_region(&hmem_active, res.start, resource_size(&res),
+			      dev_name(&pdev->dev), 0)) {
+		dev_dbg(&pdev->dev, "hmem range %pr already active\n", &res);
+		goto out_active;
+	}
+
+	pdev->dev.numa_node = numa_map_to_online_node(target_nid);
+	info = (struct memregion_info) {
+		.target_node = target_nid,
+	};
+	rc = platform_device_add_data(pdev, &info, sizeof(info));
+	if (rc < 0) {
+		pr_err("hmem memregion_info allocation failure for %pr\n", &res);
+		goto out_resource;
+	}
+
+	rc = platform_device_add_resources(pdev, &res, 1);
+	if (rc < 0) {
+		pr_err("hmem resource allocation failure for %pr\n", &res);
+		goto out_resource;
+	}
+
+	rc = platform_device_add(pdev);
+	if (rc < 0) {
+		dev_err(&pdev->dev, "device add failed for %pr\n", &res);
+		goto out_resource;
+	}
+
+	return;
+
+out_resource:
+	__release_region(&hmem_active, res.start, resource_size(&res));
+out_active:
+	platform_device_put(pdev);
+out_pdev:
+	memregion_free(id);
+}
+
+static __init int hmem_register_one(struct resource *res, void *data)
+{
+	hmem_register_device(phys_to_target_node(res->start), res);
+
+	return 0;
+}
+
+static __init int hmem_init(void)
+{
+	walk_iomem_res_desc(IORES_DESC_SOFT_RESERVED,
+			IORESOURCE_MEM, 0, -1, NULL, hmem_register_one);
+	return 0;
+}
+
+/*
+ * As this is a fallback for address ranges unclaimed by the ACPI HMAT
+ * parsing it must be at an initcall level greater than hmat_init().
+ */
+late_initcall(hmem_init);
diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
new file mode 100644
index 000000000..1bf040dbc
--- /dev/null
+++ b/drivers/dax/hmem/hmem.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/platform_device.h>
+#include <linux/memregion.h>
+#include <linux/module.h>
+#include <linux/pfn_t.h>
+#include "../bus.h"
+
+static bool region_idle;
+module_param_named(region_idle, region_idle, bool, 0644);
+
+static int dax_hmem_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct dax_region *dax_region;
+	struct memregion_info *mri;
+	struct dev_dax_data data;
+	struct dev_dax *dev_dax;
+	struct resource *res;
+	struct range range;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENOMEM;
+
+	mri = dev->platform_data;
+	range.start = res->start;
+	range.end = res->end;
+	dax_region = alloc_dax_region(dev, pdev->id, &range, mri->target_node,
+			PMD_SIZE, 0);
+	if (!dax_region)
+		return -ENOMEM;
+
+	data = (struct dev_dax_data) {
+		.dax_region = dax_region,
+		.id = -1,
+		.size = region_idle ? 0 : resource_size(res),
+	};
+	dev_dax = devm_create_dev_dax(&data);
+	if (IS_ERR(dev_dax))
+		return PTR_ERR(dev_dax);
+
+	/* child dev_dax instances now own the lifetime of the dax_region */
+	dax_region_put(dax_region);
+	return 0;
+}
+
+static int dax_hmem_remove(struct platform_device *pdev)
+{
+	/* devm handles teardown */
+	return 0;
+}
+
+static struct platform_driver dax_hmem_driver = {
+	.probe = dax_hmem_probe,
+	.remove = dax_hmem_remove,
+	.driver = {
+		.name = "hmem",
+	},
+};
+
+module_platform_driver(dax_hmem_driver);
+
+MODULE_ALIAS("platform:hmem*");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Intel Corporation");
diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
new file mode 100644
index 000000000..1a33616ce
--- /dev/null
+++ b/drivers/dax/kmem.c
@@ -0,0 +1,284 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016-2019 Intel Corporation. All rights reserved. */
+#include <linux/memremap.h>
+#include <linux/pagemap.h>
+#include <linux/memory.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/pfn_t.h>
+#include <linux/slab.h>
+#include <linux/dax.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/memory-tiers.h>
+#include "dax-private.h"
+#include "bus.h"
+
+/*
+ * Default abstract distance assigned to the NUMA node onlined
+ * by DAX/kmem if the low level platform driver didn't initialize
+ * one for this NUMA node.
+ */
+#define MEMTIER_DEFAULT_DAX_ADISTANCE	(MEMTIER_ADISTANCE_DRAM * 5)
+
+/* Memory resource name used for add_memory_driver_managed(). */
+static const char *kmem_name;
+/* Set if any memory will remain added when the driver will be unloaded. */
+static bool any_hotremove_failed;
+
+static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r)
+{
+	struct dev_dax_range *dax_range = &dev_dax->ranges[i];
+	struct range *range = &dax_range->range;
+
+	/* memory-block align the hotplug range */
+	r->start = ALIGN(range->start, memory_block_size_bytes());
+	r->end = ALIGN_DOWN(range->end + 1, memory_block_size_bytes()) - 1;
+	if (r->start >= r->end) {
+		r->start = range->start;
+		r->end = range->end;
+		return -ENOSPC;
+	}
+	return 0;
+}
+
+struct dax_kmem_data {
+	const char *res_name;
+	int mgid;
+	struct resource *res[];
+};
+
+static struct memory_dev_type *dax_slowmem_type;
+static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
+{
+	struct device *dev = &dev_dax->dev;
+	unsigned long total_len = 0;
+	struct dax_kmem_data *data;
+	int i, rc, mapped = 0;
+	int numa_node;
+
+	/*
+	 * Ensure good NUMA information for the persistent memory.
+	 * Without this check, there is a risk that slow memory
+	 * could be mixed in a node with faster memory, causing
+	 * unavoidable performance issues.
+	 */
+	numa_node = dev_dax->target_node;
+	if (numa_node < 0) {
+		dev_warn(dev, "rejecting DAX region with invalid node: %d\n",
+				numa_node);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < dev_dax->nr_range; i++) {
+		struct range range;
+
+		rc = dax_kmem_range(dev_dax, i, &range);
+		if (rc) {
+			dev_info(dev, "mapping%d: %#llx-%#llx too small after alignment\n",
+					i, range.start, range.end);
+			continue;
+		}
+		total_len += range_len(&range);
+	}
+
+	if (!total_len) {
+		dev_warn(dev, "rejecting DAX region without any memory after alignment\n");
+		return -EINVAL;
+	}
+
+	init_node_memory_type(numa_node, dax_slowmem_type);
+
+	rc = -ENOMEM;
+	data = kzalloc(struct_size(data, res, dev_dax->nr_range), GFP_KERNEL);
+	if (!data)
+		goto err_dax_kmem_data;
+
+	data->res_name = kstrdup(dev_name(dev), GFP_KERNEL);
+	if (!data->res_name)
+		goto err_res_name;
+
+	rc = memory_group_register_static(numa_node, PFN_UP(total_len));
+	if (rc < 0)
+		goto err_reg_mgid;
+	data->mgid = rc;
+
+	for (i = 0; i < dev_dax->nr_range; i++) {
+		struct resource *res;
+		struct range range;
+
+		rc = dax_kmem_range(dev_dax, i, &range);
+		if (rc)
+			continue;
+
+		/* Region is permanently reserved if hotremove fails. */
+		res = request_mem_region(range.start, range_len(&range), data->res_name);
+		if (!res) {
+			dev_warn(dev, "mapping%d: %#llx-%#llx could not reserve region\n",
+					i, range.start, range.end);
+			/*
+			 * Once some memory has been onlined we can't
+			 * assume that it can be un-onlined safely.
+			 */
+			if (mapped)
+				continue;
+			rc = -EBUSY;
+			goto err_request_mem;
+		}
+		data->res[i] = res;
+
+		/*
+		 * Set flags appropriate for System RAM.  Leave ..._BUSY clear
+		 * so that add_memory() can add a child resource.  Do not
+		 * inherit flags from the parent since it may set new flags
+		 * unknown to us that will break add_memory() below.
+		 */
+		res->flags = IORESOURCE_SYSTEM_RAM;
+
+		/*
+		 * Ensure that future kexec'd kernels will not treat
+		 * this as RAM automatically.
+		 */
+		rc = add_memory_driver_managed(data->mgid, range.start,
+				range_len(&range), kmem_name, MHP_NID_IS_MGID);
+
+		if (rc) {
+			dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
+					i, range.start, range.end);
+			remove_resource(res);
+			kfree(res);
+			data->res[i] = NULL;
+			if (mapped)
+				continue;
+			goto err_request_mem;
+		}
+		mapped++;
+	}
+
+	dev_set_drvdata(dev, data);
+
+	return 0;
+
+err_request_mem:
+	memory_group_unregister(data->mgid);
+err_reg_mgid:
+	kfree(data->res_name);
+err_res_name:
+	kfree(data);
+err_dax_kmem_data:
+	clear_node_memory_type(numa_node, dax_slowmem_type);
+	return rc;
+}
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
+{
+	int i, success = 0;
+	int node = dev_dax->target_node;
+	struct device *dev = &dev_dax->dev;
+	struct dax_kmem_data *data = dev_get_drvdata(dev);
+
+	/*
+	 * We have one shot for removing memory, if some memory blocks were not
+	 * offline prior to calling this function remove_memory() will fail, and
+	 * there is no way to hotremove this memory until reboot because device
+	 * unbind will succeed even if we return failure.
+	 */
+	for (i = 0; i < dev_dax->nr_range; i++) {
+		struct range range;
+		int rc;
+
+		rc = dax_kmem_range(dev_dax, i, &range);
+		if (rc)
+			continue;
+
+		rc = remove_memory(range.start, range_len(&range));
+		if (rc == 0) {
+			remove_resource(data->res[i]);
+			kfree(data->res[i]);
+			data->res[i] = NULL;
+			success++;
+			continue;
+		}
+		any_hotremove_failed = true;
+		dev_err(dev,
+			"mapping%d: %#llx-%#llx cannot be hotremoved until the next reboot\n",
+				i, range.start, range.end);
+	}
+
+	if (success >= dev_dax->nr_range) {
+		memory_group_unregister(data->mgid);
+		kfree(data->res_name);
+		kfree(data);
+		dev_set_drvdata(dev, NULL);
+		/*
+		 * Clear the memtype association on successful unplug.
+		 * If not, we have memory blocks left which can be
+		 * offlined/onlined later. We need to keep memory_dev_type
+		 * for that. This implies this reference will be around
+		 * till next reboot.
+		 */
+		clear_node_memory_type(node, dax_slowmem_type);
+	}
+}
+#else
+static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
+{
+	/*
+	 * Without hotremove purposely leak the request_mem_region() for the
+	 * device-dax range and return '0' to ->remove() attempts. The removal
+	 * of the device from the driver always succeeds, but the region is
+	 * permanently pinned as reserved by the unreleased
+	 * request_mem_region().
+	 */
+	any_hotremove_failed = true;
+}
+#endif /* CONFIG_MEMORY_HOTREMOVE */
+
+static struct dax_device_driver device_dax_kmem_driver = {
+	.probe = dev_dax_kmem_probe,
+	.remove = dev_dax_kmem_remove,
+};
+
+static int __init dax_kmem_init(void)
+{
+	int rc;
+
+	/* Resource name is permanently allocated if any hotremove fails. */
+	kmem_name = kstrdup_const("System RAM (kmem)", GFP_KERNEL);
+	if (!kmem_name)
+		return -ENOMEM;
+
+	dax_slowmem_type = alloc_memory_type(MEMTIER_DEFAULT_DAX_ADISTANCE);
+	if (IS_ERR(dax_slowmem_type)) {
+		rc = PTR_ERR(dax_slowmem_type);
+		goto err_dax_slowmem_type;
+	}
+
+	rc = dax_driver_register(&device_dax_kmem_driver);
+	if (rc)
+		goto error_dax_driver;
+
+	return rc;
+
+error_dax_driver:
+	destroy_memory_type(dax_slowmem_type);
+err_dax_slowmem_type:
+	kfree_const(kmem_name);
+	return rc;
+}
+
+static void __exit dax_kmem_exit(void)
+{
+	dax_driver_unregister(&device_dax_kmem_driver);
+	if (!any_hotremove_failed)
+		kfree_const(kmem_name);
+	destroy_memory_type(dax_slowmem_type);
+}
+
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL v2");
+module_init(dax_kmem_init);
+module_exit(dax_kmem_exit);
+MODULE_ALIAS_DAX_DEVICE(0);
diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
new file mode 100644
index 000000000..f050ea78b
--- /dev/null
+++ b/drivers/dax/pmem.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016 - 2018 Intel Corporation. All rights reserved. */
+#include <linux/memremap.h>
+#include <linux/module.h>
+#include <linux/pfn_t.h>
+#include "../nvdimm/pfn.h"
+#include "../nvdimm/nd.h"
+#include "bus.h"
+
+static struct dev_dax *__dax_pmem_probe(struct device *dev)
+{
+	struct range range;
+	int rc, id, region_id;
+	resource_size_t offset;
+	struct nd_pfn_sb *pfn_sb;
+	struct dev_dax *dev_dax;
+	struct dev_dax_data data;
+	struct nd_namespace_io *nsio;
+	struct dax_region *dax_region;
+	struct dev_pagemap pgmap = { };
+	struct nd_namespace_common *ndns;
+	struct nd_dax *nd_dax = to_nd_dax(dev);
+	struct nd_pfn *nd_pfn = &nd_dax->nd_pfn;
+	struct nd_region *nd_region = to_nd_region(dev->parent);
+
+	ndns = nvdimm_namespace_common_probe(dev);
+	if (IS_ERR(ndns))
+		return ERR_CAST(ndns);
+
+	/* parse the 'pfn' info block via ->rw_bytes */
+	rc = devm_namespace_enable(dev, ndns, nd_info_block_reserve());
+	if (rc)
+		return ERR_PTR(rc);
+	rc = nvdimm_setup_pfn(nd_pfn, &pgmap);
+	if (rc)
+		return ERR_PTR(rc);
+	devm_namespace_disable(dev, ndns);
+
+	/* reserve the metadata area, device-dax will reserve the data */
+	pfn_sb = nd_pfn->pfn_sb;
+	offset = le64_to_cpu(pfn_sb->dataoff);
+	nsio = to_nd_namespace_io(&ndns->dev);
+	if (!devm_request_mem_region(dev, nsio->res.start, offset,
+				dev_name(&ndns->dev))) {
+		dev_warn(dev, "could not reserve metadata\n");
+		return ERR_PTR(-EBUSY);
+	}
+
+	rc = sscanf(dev_name(&ndns->dev), "namespace%d.%d", &region_id, &id);
+	if (rc != 2)
+		return ERR_PTR(-EINVAL);
+
+	/* adjust the dax_region range to the start of data */
+	range = pgmap.range;
+	range.start += offset;
+	dax_region = alloc_dax_region(dev, region_id, &range,
+			nd_region->target_node, le32_to_cpu(pfn_sb->align),
+			IORESOURCE_DAX_STATIC);
+	if (!dax_region)
+		return ERR_PTR(-ENOMEM);
+
+	data = (struct dev_dax_data) {
+		.dax_region = dax_region,
+		.id = id,
+		.pgmap = &pgmap,
+		.size = range_len(&range),
+	};
+	dev_dax = devm_create_dev_dax(&data);
+
+	/* child dev_dax instances now own the lifetime of the dax_region */
+	dax_region_put(dax_region);
+
+	return dev_dax;
+}
+
+static int dax_pmem_probe(struct device *dev)
+{
+	return PTR_ERR_OR_ZERO(__dax_pmem_probe(dev));
+}
+
+static struct nd_device_driver dax_pmem_driver = {
+	.probe = dax_pmem_probe,
+	.drv = {
+		.name = "dax_pmem",
+	},
+	.type = ND_DRIVER_DAX_PMEM,
+};
+
+static int __init dax_pmem_init(void)
+{
+	return nd_driver_register(&dax_pmem_driver);
+}
+module_init(dax_pmem_init);
+
+static void __exit dax_pmem_exit(void)
+{
+	driver_unregister(&dax_pmem_driver.drv);
+}
+module_exit(dax_pmem_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Intel Corporation");
+MODULE_ALIAS_ND_DEVICE(ND_DEVICE_DAX_PMEM);
diff --git a/drivers/dax/pmem/Makefile b/drivers/dax/pmem/Makefile
new file mode 100644
index 000000000..191c31f0d
--- /dev/null
+++ b/drivers/dax/pmem/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem.o
+obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem_core.o
+
+dax_pmem-y := pmem.o
+dax_pmem_core-y := core.o
+dax_pmem_compat-y := compat.o
diff --git a/drivers/dax/pmem/pmem.c b/drivers/dax/pmem/pmem.c
new file mode 100644
index 000000000..dfe91a299
--- /dev/null
+++ b/drivers/dax/pmem/pmem.c
@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016 - 2018 Intel Corporation. All rights reserved. */
+#include <linux/percpu-refcount.h>
+#include <linux/memremap.h>
+#include <linux/module.h>
+#include <linux/pfn_t.h>
+#include <linux/nd.h>
+#include "../bus.h"
+
+
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
new file mode 100644
index 000000000..da4438f31
--- /dev/null
+++ b/drivers/dax/super.c
@@ -0,0 +1,594 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright(c) 2017 Intel Corporation. All rights reserved.
+ */
+#include <linux/pagemap.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/pseudo_fs.h>
+#include <linux/magic.h>
+#include <linux/pfn_t.h>
+#include <linux/cdev.h>
+#include <linux/slab.h>
+#include <linux/uio.h>
+#include <linux/dax.h>
+#include <linux/fs.h>
+#include "dax-private.h"
+
+/**
+ * struct dax_device - anchor object for dax services
+ * @inode: core vfs
+ * @cdev: optional character interface for "device dax"
+ * @private: dax driver private data
+ * @flags: state and boolean properties
+ * @ops: operations for this device
+ * @holder_data: holder of a dax_device: could be filesystem or mapped device
+ * @holder_ops: operations for the inner holder
+ */
+struct dax_device {
+	struct inode inode;
+	struct cdev cdev;
+	void *private;
+	unsigned long flags;
+	const struct dax_operations *ops;
+	void *holder_data;
+	const struct dax_holder_operations *holder_ops;
+};
+
+static dev_t dax_devt;
+DEFINE_STATIC_SRCU(dax_srcu);
+static struct vfsmount *dax_mnt;
+static DEFINE_IDA(dax_minor_ida);
+static struct kmem_cache *dax_cache __read_mostly;
+static struct super_block *dax_superblock __read_mostly;
+
+int dax_read_lock(void)
+{
+	return srcu_read_lock(&dax_srcu);
+}
+EXPORT_SYMBOL_GPL(dax_read_lock);
+
+void dax_read_unlock(int id)
+{
+	srcu_read_unlock(&dax_srcu, id);
+}
+EXPORT_SYMBOL_GPL(dax_read_unlock);
+
+#if defined(CONFIG_BLOCK) && defined(CONFIG_FS_DAX)
+#include <linux/blkdev.h>
+
+static DEFINE_XARRAY(dax_hosts);
+
+int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk)
+{
+	return xa_insert(&dax_hosts, (unsigned long)disk, dax_dev, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(dax_add_host);
+
+void dax_remove_host(struct gendisk *disk)
+{
+	xa_erase(&dax_hosts, (unsigned long)disk);
+}
+EXPORT_SYMBOL_GPL(dax_remove_host);
+
+/**
+ * fs_dax_get_by_bdev() - temporary lookup mechanism for filesystem-dax
+ * @bdev: block device to find a dax_device for
+ * @start_off: returns the byte offset into the dax_device that @bdev starts
+ * @holder: filesystem or mapped device inside the dax_device
+ * @ops: operations for the inner holder
+ */
+struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, u64 *start_off,
+		void *holder, const struct dax_holder_operations *ops)
+{
+	struct dax_device *dax_dev;
+	u64 part_size;
+	int id;
+
+	if (!blk_queue_dax(bdev->bd_disk->queue))
+		return NULL;
+
+	*start_off = get_start_sect(bdev) * SECTOR_SIZE;
+	part_size = bdev_nr_sectors(bdev) * SECTOR_SIZE;
+	if (*start_off % PAGE_SIZE || part_size % PAGE_SIZE) {
+		pr_info("%pg: error: unaligned partition for dax\n", bdev);
+		return NULL;
+	}
+
+	id = dax_read_lock();
+	dax_dev = xa_load(&dax_hosts, (unsigned long)bdev->bd_disk);
+	if (!dax_dev || !dax_alive(dax_dev) || !igrab(&dax_dev->inode))
+		dax_dev = NULL;
+	else if (holder) {
+		if (!cmpxchg(&dax_dev->holder_data, NULL, holder))
+			dax_dev->holder_ops = ops;
+		else
+			dax_dev = NULL;
+	}
+	dax_read_unlock(id);
+
+	return dax_dev;
+}
+EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
+
+void fs_put_dax(struct dax_device *dax_dev, void *holder)
+{
+	if (dax_dev && holder &&
+	    cmpxchg(&dax_dev->holder_data, holder, NULL) == holder)
+		dax_dev->holder_ops = NULL;
+	put_dax(dax_dev);
+}
+EXPORT_SYMBOL_GPL(fs_put_dax);
+#endif /* CONFIG_BLOCK && CONFIG_FS_DAX */
+
+enum dax_device_flags {
+	/* !alive + rcu grace period == no new operations / mappings */
+	DAXDEV_ALIVE,
+	/* gate whether dax_flush() calls the low level flush routine */
+	DAXDEV_WRITE_CACHE,
+	/* flag to check if device supports synchronous flush */
+	DAXDEV_SYNC,
+	/* do not leave the caches dirty after writes */
+	DAXDEV_NOCACHE,
+	/* handle CPU fetch exceptions during reads */
+	DAXDEV_NOMC,
+};
+
+/**
+ * dax_direct_access() - translate a device pgoff to an absolute pfn
+ * @dax_dev: a dax_device instance representing the logical memory range
+ * @pgoff: offset in pages from the start of the device to translate
+ * @nr_pages: number of consecutive pages caller can handle relative to @pfn
+ * @mode: indicator on normal access or recovery write
+ * @kaddr: output parameter that returns a virtual address mapping of pfn
+ * @pfn: output parameter that returns an absolute pfn translation of @pgoff
+ *
+ * Return: negative errno if an error occurs, otherwise the number of
+ * pages accessible at the device relative @pgoff.
+ */
+long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
+		enum dax_access_mode mode, void **kaddr, pfn_t *pfn)
+{
+	long avail;
+
+	if (!dax_dev)
+		return -EOPNOTSUPP;
+
+	if (!dax_alive(dax_dev))
+		return -ENXIO;
+
+	if (nr_pages < 0)
+		return -EINVAL;
+
+	avail = dax_dev->ops->direct_access(dax_dev, pgoff, nr_pages,
+			mode, kaddr, pfn);
+	if (!avail)
+		return -ERANGE;
+	return min(avail, nr_pages);
+}
+EXPORT_SYMBOL_GPL(dax_direct_access);
+
+size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
+		size_t bytes, struct iov_iter *i)
+{
+	if (!dax_alive(dax_dev))
+		return 0;
+
+	/*
+	 * The userspace address for the memory copy has already been validated
+	 * via access_ok() in vfs_write, so use the 'no check' version to bypass
+	 * the HARDENED_USERCOPY overhead.
+	 */
+	if (test_bit(DAXDEV_NOCACHE, &dax_dev->flags))
+		return _copy_from_iter_flushcache(addr, bytes, i);
+	return _copy_from_iter(addr, bytes, i);
+}
+
+size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
+		size_t bytes, struct iov_iter *i)
+{
+	if (!dax_alive(dax_dev))
+		return 0;
+
+	/*
+	 * The userspace address for the memory copy has already been validated
+	 * via access_ok() in vfs_red, so use the 'no check' version to bypass
+	 * the HARDENED_USERCOPY overhead.
+	 */
+	if (test_bit(DAXDEV_NOMC, &dax_dev->flags))
+		return _copy_mc_to_iter(addr, bytes, i);
+	return _copy_to_iter(addr, bytes, i);
+}
+
+int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
+			size_t nr_pages)
+{
+	if (!dax_alive(dax_dev))
+		return -ENXIO;
+	/*
+	 * There are no callers that want to zero more than one page as of now.
+	 * Once users are there, this check can be removed after the
+	 * device mapper code has been updated to split ranges across targets.
+	 */
+	if (nr_pages != 1)
+		return -EIO;
+
+	return dax_dev->ops->zero_page_range(dax_dev, pgoff, nr_pages);
+}
+EXPORT_SYMBOL_GPL(dax_zero_page_range);
+
+size_t dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
+		void *addr, size_t bytes, struct iov_iter *iter)
+{
+	if (!dax_dev->ops->recovery_write)
+		return 0;
+	return dax_dev->ops->recovery_write(dax_dev, pgoff, addr, bytes, iter);
+}
+EXPORT_SYMBOL_GPL(dax_recovery_write);
+
+int dax_holder_notify_failure(struct dax_device *dax_dev, u64 off,
+			      u64 len, int mf_flags)
+{
+	int rc, id;
+
+	id = dax_read_lock();
+	if (!dax_alive(dax_dev)) {
+		rc = -ENXIO;
+		goto out;
+	}
+
+	if (!dax_dev->holder_ops) {
+		rc = -EOPNOTSUPP;
+		goto out;
+	}
+
+	rc = dax_dev->holder_ops->notify_failure(dax_dev, off, len, mf_flags);
+out:
+	dax_read_unlock(id);
+	return rc;
+}
+EXPORT_SYMBOL_GPL(dax_holder_notify_failure);
+
+#ifdef CONFIG_ARCH_HAS_PMEM_API
+void arch_wb_cache_pmem(void *addr, size_t size);
+void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
+{
+	if (unlikely(!dax_write_cache_enabled(dax_dev)))
+		return;
+
+	arch_wb_cache_pmem(addr, size);
+}
+#else
+void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
+{
+}
+#endif
+EXPORT_SYMBOL_GPL(dax_flush);
+
+void dax_write_cache(struct dax_device *dax_dev, bool wc)
+{
+	if (wc)
+		set_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
+	else
+		clear_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_write_cache);
+
+bool dax_write_cache_enabled(struct dax_device *dax_dev)
+{
+	return test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
+
+bool dax_synchronous(struct dax_device *dax_dev)
+{
+	return test_bit(DAXDEV_SYNC, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_synchronous);
+
+void set_dax_synchronous(struct dax_device *dax_dev)
+{
+	set_bit(DAXDEV_SYNC, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(set_dax_synchronous);
+
+void set_dax_nocache(struct dax_device *dax_dev)
+{
+	set_bit(DAXDEV_NOCACHE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(set_dax_nocache);
+
+void set_dax_nomc(struct dax_device *dax_dev)
+{
+	set_bit(DAXDEV_NOMC, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(set_dax_nomc);
+
+bool dax_alive(struct dax_device *dax_dev)
+{
+	lockdep_assert_held(&dax_srcu);
+	return test_bit(DAXDEV_ALIVE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_alive);
+
+/*
+ * Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring
+ * that any fault handlers or operations that might have seen
+ * dax_alive(), have completed.  Any operations that start after
+ * synchronize_srcu() has run will abort upon seeing !dax_alive().
+ */
+void kill_dax(struct dax_device *dax_dev)
+{
+	if (!dax_dev)
+		return;
+
+	if (dax_dev->holder_data != NULL)
+		dax_holder_notify_failure(dax_dev, 0, U64_MAX, 0);
+
+	clear_bit(DAXDEV_ALIVE, &dax_dev->flags);
+	synchronize_srcu(&dax_srcu);
+
+	/* clear holder data */
+	dax_dev->holder_ops = NULL;
+	dax_dev->holder_data = NULL;
+}
+EXPORT_SYMBOL_GPL(kill_dax);
+
+void run_dax(struct dax_device *dax_dev)
+{
+	set_bit(DAXDEV_ALIVE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(run_dax);
+
+static struct inode *dax_alloc_inode(struct super_block *sb)
+{
+	struct dax_device *dax_dev;
+	struct inode *inode;
+
+	dax_dev = alloc_inode_sb(sb, dax_cache, GFP_KERNEL);
+	if (!dax_dev)
+		return NULL;
+
+	inode = &dax_dev->inode;
+	inode->i_rdev = 0;
+	return inode;
+}
+
+static struct dax_device *to_dax_dev(struct inode *inode)
+{
+	return container_of(inode, struct dax_device, inode);
+}
+
+static void dax_free_inode(struct inode *inode)
+{
+	struct dax_device *dax_dev = to_dax_dev(inode);
+	if (inode->i_rdev)
+		ida_free(&dax_minor_ida, iminor(inode));
+	kmem_cache_free(dax_cache, dax_dev);
+}
+
+static void dax_destroy_inode(struct inode *inode)
+{
+	struct dax_device *dax_dev = to_dax_dev(inode);
+	WARN_ONCE(test_bit(DAXDEV_ALIVE, &dax_dev->flags),
+			"kill_dax() must be called before final iput()\n");
+}
+
+static const struct super_operations dax_sops = {
+	.statfs = simple_statfs,
+	.alloc_inode = dax_alloc_inode,
+	.destroy_inode = dax_destroy_inode,
+	.free_inode = dax_free_inode,
+	.drop_inode = generic_delete_inode,
+};
+
+static int dax_init_fs_context(struct fs_context *fc)
+{
+	struct pseudo_fs_context *ctx = init_pseudo(fc, DAXFS_MAGIC);
+	if (!ctx)
+		return -ENOMEM;
+	ctx->ops = &dax_sops;
+	return 0;
+}
+
+static struct file_system_type dax_fs_type = {
+	.name		= "dax",
+	.init_fs_context = dax_init_fs_context,
+	.kill_sb	= kill_anon_super,
+};
+
+static int dax_test(struct inode *inode, void *data)
+{
+	dev_t devt = *(dev_t *) data;
+
+	return inode->i_rdev == devt;
+}
+
+static int dax_set(struct inode *inode, void *data)
+{
+	dev_t devt = *(dev_t *) data;
+
+	inode->i_rdev = devt;
+	return 0;
+}
+
+static struct dax_device *dax_dev_get(dev_t devt)
+{
+	struct dax_device *dax_dev;
+	struct inode *inode;
+
+	inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
+			dax_test, dax_set, &devt);
+
+	if (!inode)
+		return NULL;
+
+	dax_dev = to_dax_dev(inode);
+	if (inode->i_state & I_NEW) {
+		set_bit(DAXDEV_ALIVE, &dax_dev->flags);
+		inode->i_cdev = &dax_dev->cdev;
+		inode->i_mode = S_IFCHR;
+		inode->i_flags = S_DAX;
+		mapping_set_gfp_mask(&inode->i_data, GFP_USER);
+		unlock_new_inode(inode);
+	}
+
+	return dax_dev;
+}
+
+struct dax_device *alloc_dax(void *private, const struct dax_operations *ops)
+{
+	struct dax_device *dax_dev;
+	dev_t devt;
+	int minor;
+
+	if (WARN_ON_ONCE(ops && !ops->zero_page_range))
+		return ERR_PTR(-EINVAL);
+
+	minor = ida_alloc_max(&dax_minor_ida, MINORMASK, GFP_KERNEL);
+	if (minor < 0)
+		return ERR_PTR(-ENOMEM);
+
+	devt = MKDEV(MAJOR(dax_devt), minor);
+	dax_dev = dax_dev_get(devt);
+	if (!dax_dev)
+		goto err_dev;
+
+	dax_dev->ops = ops;
+	dax_dev->private = private;
+	return dax_dev;
+
+ err_dev:
+	ida_free(&dax_minor_ida, minor);
+	return ERR_PTR(-ENOMEM);
+}
+EXPORT_SYMBOL_GPL(alloc_dax);
+
+void put_dax(struct dax_device *dax_dev)
+{
+	if (!dax_dev)
+		return;
+	iput(&dax_dev->inode);
+}
+EXPORT_SYMBOL_GPL(put_dax);
+
+/**
+ * dax_holder() - obtain the holder of a dax device
+ * @dax_dev: a dax_device instance
+
+ * Return: the holder's data which represents the holder if registered,
+ * otherwize NULL.
+ */
+void *dax_holder(struct dax_device *dax_dev)
+{
+	return dax_dev->holder_data;
+}
+EXPORT_SYMBOL_GPL(dax_holder);
+
+/**
+ * inode_dax: convert a public inode into its dax_dev
+ * @inode: An inode with i_cdev pointing to a dax_dev
+ *
+ * Note this is not equivalent to to_dax_dev() which is for private
+ * internal use where we know the inode filesystem type == dax_fs_type.
+ */
+struct dax_device *inode_dax(struct inode *inode)
+{
+	struct cdev *cdev = inode->i_cdev;
+
+	return container_of(cdev, struct dax_device, cdev);
+}
+EXPORT_SYMBOL_GPL(inode_dax);
+
+struct inode *dax_inode(struct dax_device *dax_dev)
+{
+	return &dax_dev->inode;
+}
+EXPORT_SYMBOL_GPL(dax_inode);
+
+void *dax_get_private(struct dax_device *dax_dev)
+{
+	if (!test_bit(DAXDEV_ALIVE, &dax_dev->flags))
+		return NULL;
+	return dax_dev->private;
+}
+EXPORT_SYMBOL_GPL(dax_get_private);
+
+static void init_once(void *_dax_dev)
+{
+	struct dax_device *dax_dev = _dax_dev;
+	struct inode *inode = &dax_dev->inode;
+
+	memset(dax_dev, 0, sizeof(*dax_dev));
+	inode_init_once(inode);
+}
+
+static int dax_fs_init(void)
+{
+	int rc;
+
+	dax_cache = kmem_cache_create("dax_cache", sizeof(struct dax_device), 0,
+			(SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
+			 SLAB_MEM_SPREAD|SLAB_ACCOUNT),
+			init_once);
+	if (!dax_cache)
+		return -ENOMEM;
+
+	dax_mnt = kern_mount(&dax_fs_type);
+	if (IS_ERR(dax_mnt)) {
+		rc = PTR_ERR(dax_mnt);
+		goto err_mount;
+	}
+	dax_superblock = dax_mnt->mnt_sb;
+
+	return 0;
+
+ err_mount:
+	kmem_cache_destroy(dax_cache);
+
+	return rc;
+}
+
+static void dax_fs_exit(void)
+{
+	kern_unmount(dax_mnt);
+	rcu_barrier();
+	kmem_cache_destroy(dax_cache);
+}
+
+static int __init dax_core_init(void)
+{
+	int rc;
+
+	rc = dax_fs_init();
+	if (rc)
+		return rc;
+
+	rc = alloc_chrdev_region(&dax_devt, 0, MINORMASK+1, "dax");
+	if (rc)
+		goto err_chrdev;
+
+	rc = dax_bus_init();
+	if (rc)
+		goto err_bus;
+	return 0;
+
+err_bus:
+	unregister_chrdev_region(dax_devt, MINORMASK+1);
+err_chrdev:
+	dax_fs_exit();
+	return 0;
+}
+
+static void __exit dax_core_exit(void)
+{
+	dax_bus_exit();
+	unregister_chrdev_region(dax_devt, MINORMASK+1);
+	ida_destroy(&dax_minor_ida);
+	dax_fs_exit();
+}
+
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL v2");
+subsys_initcall(dax_core_init);
+module_exit(dax_core_exit);