Adding upstream version 6.6.15.upstream/6.6.15

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

1 files changed, 1487 insertions, 0 deletions

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
new file mode 100644
index 0000000000..0ee96e6fc4
--- /dev/null
+++ b/drivers/dax/bus.c
@@ -0,0 +1,1487 @@
+// 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(const 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;
+}
+
+static int dax_match_type(struct dax_device_driver *dax_drv, struct device *dev)
+{
+	enum dax_driver_type type = DAXDRV_DEVICE_TYPE;
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+
+	if (dev_dax->region->res.flags & IORESOURCE_DAX_KMEM)
+		type = DAXDRV_KMEM_TYPE;
+
+	if (dax_drv->type == type)
+		return 1;
+
+	/* default to device mode if dax_kmem is disabled */
+	if (dax_drv->type == DAXDRV_DEVICE_TYPE &&
+	    !IS_ENABLED(CONFIG_DEV_DAX_KMEM))
+		return 1;
+
+	return 0;
+}
+
+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);
+
+	if (dax_match_id(dax_drv, dev))
+		return 1;
+	return dax_match_type(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);
+}
+
+static void dax_region_put(struct dax_region *dax_region)
+{
+	kref_put(&dax_region->kref, dax_region_free);
+}
+
+/* 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;
+	}
+
+	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_unregister(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);
+
+int __dax_driver_register(struct dax_device_driver *dax_drv,
+		struct module *module, const char *mod_name)
+{
+	struct device_driver *drv = &dax_drv->drv;
+
+	/*
+	 * 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;
+
+	return driver_register(drv);
+}
+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);
+	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);
+}