// 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);

/*
 * All changes to the dax region configuration occur with this lock held
 * for write.
 */
DECLARE_RWSEM(dax_region_rwsem);

/*
 * All changes to the dax device configuration occur with this lock held
 * for write.
 */
DECLARE_RWSEM(dax_dev_rwsem);

#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);
}

#define to_dax_drv(__drv)       container_of_const(__drv, struct dax_device_driver, drv)

static struct dax_id *__dax_match_id(const 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(const 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(const 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_obj(*dax_id);
                        if (dax_id) {
                                strscpy(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, const 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;

        lockdep_assert_held(&dax_dev_rwsem);

        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;
        u64 size;

        rc = down_read_interruptible(&dax_dev_rwsem);
        if (rc)
                return rc;
        size = dev_dax_size(dev_dax);
        up_read(&dax_dev_rwsem);

        if (size == 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 const 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, const struct device_driver *drv)
{
        const 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 sysfs_emit(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 sysfs_emit(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 sysfs_emit(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;

        lockdep_assert_held(&dax_region_rwsem);

        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;
        int rc;

        rc = down_read_interruptible(&dax_region_rwsem);
        if (rc)
                return rc;
        size = dax_region_avail_size(dax_region);
        up_read(&dax_region_rwsem);

        return sysfs_emit(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;

        rc = down_read_interruptible(&dax_region_rwsem);
        if (rc)
                return rc;
        seed = dax_region->seed;
        rc = sysfs_emit(buf, "%s\n", seed ? dev_name(seed) : "");
        up_read(&dax_region_rwsem);

        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;

        rc = down_read_interruptible(&dax_region_rwsem);
        if (rc)
                return rc;
        youngest = dax_region->youngest;
        rc = sysfs_emit(buf, "%s\n", youngest ? dev_name(youngest) : "");
        up_read(&dax_region_rwsem);

        return rc;
}

static struct dev_dax *__devm_create_dev_dax(struct dev_dax_data *data);

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;

        rc = down_write_killable(&dax_region_rwsem);
        if (rc)
                return rc;
        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,
                        .memmap_on_memory = false,
                };
                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;
                }
        }
        up_write(&dax_region_rwsem);

        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;

        lockdep_assert_held_write(&dax_region_rwsem);
        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__);

        down_write(&dax_region_rwsem);
        kill_dev_dax(dev_dax);
        device_del(dev);
        free_dev_dax_ranges(dev_dax);
        put_device(dev);
        up_write(&dax_region_rwsem);
}

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 dax_region *dax_region;
        int rc = dev_dax->id;

        lockdep_assert_held_write(&dax_dev_rwsem);

        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)
{
        int rc;

        rc = down_write_killable(&dax_dev_rwsem);
        if (rc)
                return rc;
        rc = __free_dev_dax_id(dev_dax);
        up_write(&dax_dev_rwsem);
        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);
        down_write(&dax_dev_rwsem);
        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;
        }
        up_write(&dax_dev_rwsem);
        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_obj(*dax_region);
        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);

        dev_dbg(dev, "%s\n", __func__);

        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);
        int rc;

        rc = down_write_killable(&dax_region_rwsem);
        if (rc)
                return NULL;
        if (mapping->range_id < 0) {
                up_write(&dax_region_rwsem);
                return NULL;
        }

        return &dev_dax->ranges[mapping->range_id];
}

static void put_dax_range(void)
{
        up_write(&dax_region_rwsem);
}

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 = sysfs_emit(buf, "%#llx\n", dax_range->range.start);
        put_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 = sysfs_emit(buf, "%#llx\n", dax_range->range.end);
        put_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 = sysfs_emit(buf, "%#lx\n", dax_range->pgoff);
        put_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 const 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;

        lockdep_assert_held_write(&dax_region_rwsem);

        if (dev_WARN_ONCE(&dev_dax->dev, !dax_region->dev->driver,
                                "region disabled\n"))
                return -ENXIO;

        mapping = kzalloc_obj(*mapping);
        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;

        lockdep_assert_held_write(&dax_region_rwsem);

        /* 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];
        bool is_shrink = resource_size(res) > size;
        struct range *range = &dax_range->range;
        struct device *dev = &dev_dax->dev;
        int rc;

        lockdep_assert_held_write(&dax_region_rwsem);

        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;
        int rc;

        rc = down_read_interruptible(&dax_dev_rwsem);
        if (rc)
                return rc;
        size = dev_dax_size(dev_dax);
        up_read(&dax_dev_rwsem);

        return sysfs_emit(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;
        }

        rc = down_write_killable(&dax_region_rwsem);
        if (rc)
                return rc;
        if (!dax_region->dev->driver) {
                rc = -ENXIO;
                goto err_region;
        }
        rc = down_write_killable(&dax_dev_rwsem);
        if (rc)
                goto err_dev;

        rc = dev_dax_resize(dax_region, dev_dax, val);

err_dev:
        up_write(&dax_dev_rwsem);
err_region:
        up_write(&dax_region_rwsem);

        if (rc == 0)
                return len;
        return 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 = down_write_killable(&dax_region_rwsem);
        if (rc)
                return rc;
        if (!dax_region->dev->driver) {
                up_write(&dax_region_rwsem);
                return rc;
        }
        rc = down_write_killable(&dax_dev_rwsem);
        if (rc) {
                up_write(&dax_region_rwsem);
                return rc;
        }

        to_alloc = range_len(&r);
        if (alloc_is_aligned(dev_dax, to_alloc))
                rc = alloc_dev_dax_range(dev_dax, r.start, to_alloc);
        up_write(&dax_dev_rwsem);
        up_write(&dax_region_rwsem);

        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 sysfs_emit(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;

        rc = down_write_killable(&dax_region_rwsem);
        if (rc)
                return rc;
        if (!dax_region->dev->driver) {
                up_write(&dax_region_rwsem);
                return -ENXIO;
        }

        rc = down_write_killable(&dax_dev_rwsem);
        if (rc) {
                up_write(&dax_region_rwsem);
                return rc;
        }
        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:
        up_write(&dax_dev_rwsem);
        up_write(&dax_region_rwsem);
        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 sysfs_emit(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 sysfs_emit(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 sysfs_emit(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 sysfs_emit(buf, "%d\n", dev_to_node(dev));
}
static DEVICE_ATTR_RO(numa_node);

static ssize_t memmap_on_memory_show(struct device *dev,
                                     struct device_attribute *attr, char *buf)
{
        struct dev_dax *dev_dax = to_dev_dax(dev);

        return sysfs_emit(buf, "%d\n", dev_dax->memmap_on_memory);
}

static ssize_t memmap_on_memory_store(struct device *dev,
                                      struct device_attribute *attr,
                                      const char *buf, size_t len)
{
        struct dev_dax *dev_dax = to_dev_dax(dev);
        bool val;
        int rc;

        rc = kstrtobool(buf, &val);
        if (rc)
                return rc;

        if (val == true && !mhp_supports_memmap_on_memory()) {
                dev_dbg(dev, "memmap_on_memory is not available\n");
                return -EOPNOTSUPP;
        }

        rc = down_write_killable(&dax_dev_rwsem);
        if (rc)
                return rc;

        if (dev_dax->memmap_on_memory != val && dev->driver &&
            to_dax_drv(dev->driver)->type == DAXDRV_KMEM_TYPE) {
                up_write(&dax_dev_rwsem);
                return -EBUSY;
        }

        dev_dax->memmap_on_memory = val;
        up_write(&dax_dev_rwsem);

        return len;
}
static DEVICE_ATTR_RW(memmap_on_memory);

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,
        &dev_attr_memmap_on_memory.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,
};

static 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_obj(*dev_dax);
        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);

        dev_dax->memmap_on_memory = data->memmap_on_memory;

        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);
}

struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
{
        struct dev_dax *dev_dax;

        down_write(&dax_region_rwsem);
        dev_dax = __devm_create_dev_dax(data);
        up_write(&dax_region_rwsem);

        return dev_dax;
}
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);
}