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    Subject[PATCH 02/15] libnvdimm: infrastructure for btt devices
    From
    Date
    Block devices from an nd bus, in addition to accepting "struct bio"
    based requests, also have the capability to perform byte-aligned
    accesses. By default only the bio/block interface is used. However, if
    another driver can make effective use of the byte-aligned capability it
    can claim the block interface and use the byte-aligned ->rw_bytes()
    interface.

    The BTT driver is the initial first consumer of this mechanism to allow
    layering atomic sector update guarantees on top of ->rw_bytes() capable
    libnvdimm-block-devices, or their partitions.

    Cc: Greg KH <gregkh@linuxfoundation.org>
    Cc: Neil Brown <neilb@suse.de>
    Signed-off-by: Dan Williams <dan.j.williams@intel.com>
    ---
    drivers/nvdimm/Kconfig | 3
    drivers/nvdimm/Makefile | 1
    drivers/nvdimm/btt.h | 45 +++++
    drivers/nvdimm/btt_devs.c | 431 ++++++++++++++++++++++++++++++++++++++++++++
    drivers/nvdimm/bus.c | 82 ++++++++
    drivers/nvdimm/core.c | 20 ++
    drivers/nvdimm/nd-core.h | 34 +++
    drivers/nvdimm/nd.h | 19 ++
    drivers/nvdimm/pmem.c | 6 -
    include/uapi/linux/ndctl.h | 2
    10 files changed, 637 insertions(+), 6 deletions(-)
    create mode 100644 drivers/nvdimm/btt.h
    create mode 100644 drivers/nvdimm/btt_devs.c

    diff --git a/drivers/nvdimm/Kconfig b/drivers/nvdimm/Kconfig
    index 07a29113b870..f16ba9d14740 100644
    --- a/drivers/nvdimm/Kconfig
    +++ b/drivers/nvdimm/Kconfig
    @@ -33,4 +33,7 @@ config BLK_DEV_PMEM

    Say Y if you want to use an NVDIMM

    +config ND_BTT_DEVS
    + def_bool y
    +
    endif
    diff --git a/drivers/nvdimm/Makefile b/drivers/nvdimm/Makefile
    index abce98f87f16..eb1bbce86592 100644
    --- a/drivers/nvdimm/Makefile
    +++ b/drivers/nvdimm/Makefile
    @@ -11,3 +11,4 @@ libnvdimm-y += region_devs.o
    libnvdimm-y += region.o
    libnvdimm-y += namespace_devs.o
    libnvdimm-y += label.o
    +libnvdimm-$(CONFIG_ND_BTT_DEVS) += btt_devs.o
    diff --git a/drivers/nvdimm/btt.h b/drivers/nvdimm/btt.h
    new file mode 100644
    index 000000000000..e8f6d8e0ddd3
    --- /dev/null
    +++ b/drivers/nvdimm/btt.h
    @@ -0,0 +1,45 @@
    +/*
    + * Block Translation Table library
    + * Copyright (c) 2014-2015, Intel Corporation.
    + *
    + * This program is free software; you can redistribute it and/or modify it
    + * under the terms and conditions of the GNU General Public License,
    + * version 2, as published by the Free Software Foundation.
    + *
    + * This program is distributed in the hope it will be useful, but WITHOUT
    + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
    + * more details.
    + */
    +
    +#ifndef _LINUX_BTT_H
    +#define _LINUX_BTT_H
    +
    +#include <linux/types.h>
    +
    +#define BTT_SIG_LEN 16
    +#define BTT_SIG "BTT_ARENA_INFO\0"
    +
    +struct btt_sb {
    + u8 signature[BTT_SIG_LEN];
    + u8 uuid[16];
    + u8 parent_uuid[16];
    + __le32 flags;
    + __le16 version_major;
    + __le16 version_minor;
    + __le32 external_lbasize;
    + __le32 external_nlba;
    + __le32 internal_lbasize;
    + __le32 internal_nlba;
    + __le32 nfree;
    + __le32 infosize;
    + __le64 nextoff;
    + __le64 dataoff;
    + __le64 mapoff;
    + __le64 logoff;
    + __le64 info2off;
    + u8 padding[3968];
    + __le64 checksum;
    +};
    +
    +#endif
    diff --git a/drivers/nvdimm/btt_devs.c b/drivers/nvdimm/btt_devs.c
    new file mode 100644
    index 000000000000..2148fd8f535b
    --- /dev/null
    +++ b/drivers/nvdimm/btt_devs.c
    @@ -0,0 +1,431 @@
    +/*
    + * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
    + *
    + * This program is free software; you can redistribute it and/or modify
    + * it under the terms of version 2 of the GNU General Public License as
    + * published by the Free Software Foundation.
    + *
    + * This program is distributed in the hope that it will be useful, but
    + * WITHOUT ANY WARRANTY; without even the implied warranty of
    + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    + * General Public License for more details.
    + */
    +#include <linux/blkdev.h>
    +#include <linux/device.h>
    +#include <linux/genhd.h>
    +#include <linux/sizes.h>
    +#include <linux/slab.h>
    +#include <linux/fs.h>
    +#include <linux/mm.h>
    +#include "nd-core.h"
    +#include "btt.h"
    +#include "nd.h"
    +
    +static DEFINE_IDA(btt_ida);
    +
    +static void nd_btt_release(struct device *dev)
    +{
    + struct nd_btt *nd_btt = to_nd_btt(dev);
    +
    + dev_dbg(dev, "%s\n", __func__);
    + WARN_ON(nd_btt->backing_dev);
    + ida_simple_remove(&btt_ida, nd_btt->id);
    + kfree(nd_btt->uuid);
    + kfree(nd_btt);
    +}
    +
    +static struct device_type nd_btt_device_type = {
    + .name = "nd_btt",
    + .release = nd_btt_release,
    +};
    +
    +bool is_nd_btt(struct device *dev)
    +{
    + return dev->type == &nd_btt_device_type;
    +}
    +
    +struct nd_btt *to_nd_btt(struct device *dev)
    +{
    + struct nd_btt *nd_btt = container_of(dev, struct nd_btt, dev);
    +
    + WARN_ON(!is_nd_btt(dev));
    + return nd_btt;
    +}
    +EXPORT_SYMBOL(to_nd_btt);
    +
    +static const unsigned long btt_lbasize_supported[] = { 512, 4096, 0 };
    +
    +static ssize_t sector_size_show(struct device *dev,
    + struct device_attribute *attr, char *buf)
    +{
    + struct nd_btt *nd_btt = to_nd_btt(dev);
    +
    + return nd_sector_size_show(nd_btt->lbasize, btt_lbasize_supported, buf);
    +}
    +
    +static ssize_t sector_size_store(struct device *dev,
    + struct device_attribute *attr, const char *buf, size_t len)
    +{
    + struct nd_btt *nd_btt = to_nd_btt(dev);
    + ssize_t rc;
    +
    + device_lock(dev);
    + nvdimm_bus_lock(dev);
    + rc = nd_sector_size_store(dev, buf, &nd_btt->lbasize,
    + btt_lbasize_supported);
    + dev_dbg(dev, "%s: result: %zd wrote: %s%s", __func__,
    + rc, buf, buf[len - 1] == '\n' ? "" : "\n");
    + nvdimm_bus_unlock(dev);
    + device_unlock(dev);
    +
    + return rc ? rc : len;
    +}
    +static DEVICE_ATTR_RW(sector_size);
    +
    +static ssize_t uuid_show(struct device *dev,
    + struct device_attribute *attr, char *buf)
    +{
    + struct nd_btt *nd_btt = to_nd_btt(dev);
    +
    + if (nd_btt->uuid)
    + return sprintf(buf, "%pUb\n", nd_btt->uuid);
    + return sprintf(buf, "\n");
    +}
    +
    +static ssize_t uuid_store(struct device *dev,
    + struct device_attribute *attr, const char *buf, size_t len)
    +{
    + struct nd_btt *nd_btt = to_nd_btt(dev);
    + ssize_t rc;
    +
    + device_lock(dev);
    + rc = nd_uuid_store(dev, &nd_btt->uuid, buf, len);
    + dev_dbg(dev, "%s: result: %zd wrote: %s%s", __func__,
    + rc, buf, buf[len - 1] == '\n' ? "" : "\n");
    + device_unlock(dev);
    +
    + return rc ? rc : len;
    +}
    +static DEVICE_ATTR_RW(uuid);
    +
    +static ssize_t backing_dev_show(struct device *dev,
    + struct device_attribute *attr, char *buf)
    +{
    + struct nd_btt *nd_btt = to_nd_btt(dev);
    + char name[BDEVNAME_SIZE];
    +
    + if (nd_btt->backing_dev)
    + return sprintf(buf, "/dev/%s\n",
    + bdevname(nd_btt->backing_dev, name));
    + else
    + return sprintf(buf, "\n");
    +}
    +
    +static const fmode_t nd_btt_devs_mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
    +
    +static void nd_btt_remove_bdev(struct nd_btt *nd_btt, const char *caller)
    +{
    + struct block_device *bdev = nd_btt->backing_dev;
    + char bdev_name[BDEVNAME_SIZE];
    +
    + if (!nd_btt->backing_dev)
    + return;
    +
    + WARN_ON_ONCE(!is_nvdimm_bus_locked(&nd_btt->dev));
    + dev_dbg(&nd_btt->dev, "%s: %s: release %s\n", caller, __func__,
    + bdevname(bdev, bdev_name));
    + blkdev_put(bdev, nd_btt_devs_mode);
    + nd_btt->backing_dev = NULL;
    +
    + /*
    + * Once we've had our backing device removed we need to be fully
    + * reconfigured. The bus will have already created a new seed
    + * for this purpose, so now is a good time to clean up this
    + * stale nd_btt instance.
    + */
    + if (nd_btt->dev.driver)
    + nd_device_unregister(&nd_btt->dev, ND_ASYNC);
    +}
    +
    +static int __nd_btt_remove_disk(struct device *dev, void *data)
    +{
    + struct gendisk *disk = data;
    + struct block_device *bdev;
    + struct nd_btt *nd_btt;
    +
    + if (!is_nd_btt(dev))
    + return 0;
    +
    + nd_btt = to_nd_btt(dev);
    + bdev = nd_btt->backing_dev;
    + if (bdev && bdev->bd_disk == disk)
    + nd_btt_remove_bdev(nd_btt, __func__);
    + return 0;
    +}
    +
    +void nd_btt_remove_disk(struct nvdimm_bus *nvdimm_bus, struct gendisk *disk)
    +{
    + device_for_each_child(&nvdimm_bus->dev, disk, __nd_btt_remove_disk);
    +}
    +
    +static ssize_t __backing_dev_store(struct device *dev,
    + struct device_attribute *attr, const char *buf, size_t len)
    +{
    + struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(dev);
    + const struct block_device_operations *ops;
    + struct nd_btt *nd_btt = to_nd_btt(dev);
    + struct block_device *bdev;
    + char *path;
    +
    + if (dev->driver) {
    + dev_dbg(dev, "%s: -EBUSY\n", __func__);
    + return -EBUSY;
    + }
    +
    + path = kstrndup(buf, len, GFP_KERNEL);
    + if (!path)
    + return -ENOMEM;
    + strim(path);
    +
    + /* detach the backing device */
    + if (strcmp(path, "") == 0) {
    + nd_btt_remove_bdev(nd_btt, __func__);
    + goto out;
    + } else if (nd_btt->backing_dev) {
    + dev_dbg(dev, "backing_dev already set\n");
    + len = -EBUSY;
    + goto out;
    + }
    +
    + bdev = blkdev_get_by_path(path, nd_btt_devs_mode, nd_btt);
    + if (IS_ERR(bdev)) {
    + dev_dbg(dev, "open '%s' failed: %ld\n", path, PTR_ERR(bdev));
    + len = PTR_ERR(bdev);
    + goto out;
    + }
    +
    + if (nvdimm_bus != walk_to_nvdimm_bus(disk_to_dev(bdev->bd_disk))) {
    + dev_dbg(dev, "%s not a descendant of %s\n", path,
    + dev_name(&nvdimm_bus->dev));
    + blkdev_put(bdev, nd_btt_devs_mode);
    + len = -EINVAL;
    + goto out;
    + }
    +
    + if (get_capacity(bdev->bd_disk) < SZ_16M / 512) {
    + dev_dbg(dev, "%s too small to host btt\n", path);
    + blkdev_put(bdev, nd_btt_devs_mode);
    + len = -ENXIO;
    + goto out;
    + }
    +
    + ops = bdev->bd_disk->fops;
    + if (!ops->rw_bytes) {
    + dev_dbg(dev, "%s does not implement ->rw_bytes()\n", path);
    + blkdev_put(bdev, nd_btt_devs_mode);
    + len = -EINVAL;
    + goto out;
    + }
    +
    + WARN_ON_ONCE(!is_nvdimm_bus_locked(&nd_btt->dev));
    + nd_btt->backing_dev = bdev;
    +
    + out:
    + kfree(path);
    + return len;
    +}
    +
    +static ssize_t backing_dev_store(struct device *dev,
    + struct device_attribute *attr, const char *buf, size_t len)
    +{
    + ssize_t rc;
    +
    + nvdimm_bus_lock(dev);
    + device_lock(dev);
    + rc = __backing_dev_store(dev, attr, buf, len);
    + dev_dbg(dev, "%s: result: %zd wrote: %s%s", __func__,
    + rc, buf, buf[len - 1] == '\n' ? "" : "\n");
    + device_unlock(dev);
    + nvdimm_bus_unlock(dev);
    +
    + return rc;
    +}
    +static DEVICE_ATTR_RW(backing_dev);
    +
    +static bool is_nd_btt_idle(struct device *dev)
    +{
    + struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(dev);
    + struct nd_btt *nd_btt = to_nd_btt(dev);
    +
    + if (nvdimm_bus->nd_btt == nd_btt || dev->driver || nd_btt->backing_dev)
    + return false;
    + return true;
    +}
    +
    +static ssize_t delete_show(struct device *dev,
    + struct device_attribute *attr, char *buf)
    +{
    + /* return 1 if can be deleted */
    + return sprintf(buf, "%d\n", is_nd_btt_idle(dev));
    +}
    +
    +static ssize_t delete_store(struct device *dev,
    + struct device_attribute *attr, const char *buf, size_t len)
    +{
    + unsigned long val;
    +
    + /* write 1 to delete */
    + if (kstrtoul(buf, 0, &val) != 0 || val != 1)
    + return -EINVAL;
    +
    + /* prevent deletion while this btt is active, or is the current seed */
    + if (!is_nd_btt_idle(dev))
    + return -EBUSY;
    +
    + /*
    + * userspace raced itself if device goes active here and it gets
    + * to keep the pieces
    + */
    + nd_device_unregister(dev, ND_ASYNC);
    +
    + return len;
    +}
    +static DEVICE_ATTR_RW(delete);
    +
    +static struct attribute *nd_btt_attributes[] = {
    + &dev_attr_sector_size.attr,
    + &dev_attr_backing_dev.attr,
    + &dev_attr_delete.attr,
    + &dev_attr_uuid.attr,
    + NULL,
    +};
    +
    +static struct attribute_group nd_btt_attribute_group = {
    + .attrs = nd_btt_attributes,
    +};
    +
    +static const struct attribute_group *nd_btt_attribute_groups[] = {
    + &nd_btt_attribute_group,
    + &nd_device_attribute_group,
    + NULL,
    +};
    +
    +static struct nd_btt *__nd_btt_create(struct nvdimm_bus *nvdimm_bus,
    + unsigned long lbasize, u8 *uuid, struct block_device *bdev)
    +{
    + struct nd_btt *nd_btt = kzalloc(sizeof(*nd_btt), GFP_KERNEL);
    + struct device *dev;
    +
    + if (!nd_btt)
    + return NULL;
    + nd_btt->id = ida_simple_get(&btt_ida, 0, 0, GFP_KERNEL);
    + if (nd_btt->id < 0) {
    + kfree(nd_btt);
    + return NULL;
    + }
    +
    + nd_btt->lbasize = lbasize;
    + if (uuid)
    + uuid = kmemdup(uuid, 16, GFP_KERNEL);
    + nd_btt->uuid = uuid;
    + nd_btt->backing_dev = bdev;
    + dev = &nd_btt->dev;
    + dev_set_name(dev, "btt%d", nd_btt->id);
    + dev->parent = &nvdimm_bus->dev;
    + dev->type = &nd_btt_device_type;
    + dev->groups = nd_btt_attribute_groups;
    + nd_device_register(&nd_btt->dev);
    + return nd_btt;
    +}
    +
    +struct nd_btt *nd_btt_create(struct nvdimm_bus *nvdimm_bus)
    +{
    + return __nd_btt_create(nvdimm_bus, 0, NULL, NULL);
    +}
    +
    +/*
    + * nd_btt_sb_checksum: compute checksum for btt info block
    + *
    + * Returns a fletcher64 checksum of everything in the given info block
    + * except the last field (since that's where the checksum lives).
    + */
    +u64 nd_btt_sb_checksum(struct btt_sb *btt_sb)
    +{
    + u64 sum, sum_save;
    +
    + sum_save = btt_sb->checksum;
    + btt_sb->checksum = 0;
    + sum = nd_fletcher64(btt_sb, sizeof(*btt_sb), 1);
    + btt_sb->checksum = sum_save;
    + return sum;
    +}
    +EXPORT_SYMBOL(nd_btt_sb_checksum);
    +
    +static struct nd_btt *__nd_btt_autodetect(struct nvdimm_bus *nvdimm_bus,
    + struct block_device *bdev, struct btt_sb *btt_sb)
    +{
    + u64 checksum;
    + u32 lbasize;
    +
    + if (!btt_sb || !bdev || !nvdimm_bus)
    + return NULL;
    +
    + if (bdev_read_bytes(bdev, SZ_4K, btt_sb, sizeof(*btt_sb)))
    + return NULL;
    +
    + if (get_capacity(bdev->bd_disk) < SZ_16M / 512)
    + return NULL;
    +
    + if (memcmp(btt_sb->signature, BTT_SIG, BTT_SIG_LEN) != 0)
    + return NULL;
    +
    + checksum = le64_to_cpu(btt_sb->checksum);
    + btt_sb->checksum = 0;
    + if (checksum != nd_btt_sb_checksum(btt_sb))
    + return NULL;
    + btt_sb->checksum = cpu_to_le64(checksum);
    +
    + lbasize = le32_to_cpu(btt_sb->external_lbasize);
    + return __nd_btt_create(nvdimm_bus, lbasize, btt_sb->uuid, bdev);
    +}
    +
    +static int nd_btt_autodetect(struct nvdimm_bus *nvdimm_bus,
    + struct block_device *bdev)
    +{
    + char name[BDEVNAME_SIZE];
    + struct nd_btt *nd_btt;
    + struct btt_sb *btt_sb;
    +
    + btt_sb = kzalloc(sizeof(*btt_sb), GFP_KERNEL);
    + nd_btt = __nd_btt_autodetect(nvdimm_bus, bdev, btt_sb);
    + kfree(btt_sb);
    + dev_dbg(&nvdimm_bus->dev, "%s: %s btt: %s\n", __func__,
    + bdevname(bdev, name), nd_btt
    + ? dev_name(&nd_btt->dev) : "<none>");
    + return nd_btt ? 0 : -ENODEV;
    +}
    +
    +void nd_btt_add_disk(struct nvdimm_bus *nvdimm_bus, struct gendisk *disk)
    +{
    + struct disk_part_iter piter;
    + struct hd_struct *part;
    +
    + disk_part_iter_init(&piter, disk, DISK_PITER_INCL_PART0);
    + while ((part = disk_part_iter_next(&piter))) {
    + struct block_device *bdev;
    + int rc;
    +
    + bdev = bdget_disk(disk, part->partno);
    + if (!bdev)
    + continue;
    + if (blkdev_get(bdev, nd_btt_devs_mode, nvdimm_bus) != 0)
    + continue;
    + rc = nd_btt_autodetect(nvdimm_bus, bdev);
    + if (rc)
    + blkdev_put(bdev, nd_btt_devs_mode);
    + /* no need to scan further in the case of whole disk btt */
    + if (rc == 0 && part->partno == 0)
    + break;
    + }
    + disk_part_iter_exit(&piter);
    +}
    diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
    index ca802702440e..3c14fee5aff4 100644
    --- a/drivers/nvdimm/bus.c
    +++ b/drivers/nvdimm/bus.c
    @@ -14,8 +14,10 @@
    #include <linux/vmalloc.h>
    #include <linux/uaccess.h>
    #include <linux/module.h>
    +#include <linux/blkdev.h>
    #include <linux/fcntl.h>
    #include <linux/async.h>
    +#include <linux/genhd.h>
    #include <linux/ndctl.h>
    #include <linux/sched.h>
    #include <linux/slab.h>
    @@ -40,6 +42,8 @@ static int to_nd_device_type(struct device *dev)
    return ND_DEVICE_REGION_BLK;
    else if (is_nd_pmem(dev->parent) || is_nd_blk(dev->parent))
    return nd_region_to_nstype(to_nd_region(dev->parent));
    + else if (is_nd_btt(dev))
    + return ND_DEVICE_BTT;

    return 0;
    }
    @@ -103,6 +107,21 @@ static int nvdimm_bus_probe(struct device *dev)

    dev_dbg(&nvdimm_bus->dev, "%s.probe(%s) = %d\n", dev->driver->name,
    dev_name(dev), rc);
    +
    + /* check if our btt-seed has sprouted, and plant another */
    + if (rc == 0 && is_nd_btt(dev) && dev == &nvdimm_bus->nd_btt->dev) {
    + const char *sep = "", *name = "", *status = "failed";
    +
    + nvdimm_bus->nd_btt = nd_btt_create(nvdimm_bus);
    + if (nvdimm_bus->nd_btt) {
    + status = "succeeded";
    + sep = ": ";
    + name = dev_name(&nvdimm_bus->nd_btt->dev);
    + }
    + dev_dbg(&nvdimm_bus->dev, "btt seed creation %s%s%s\n",
    + status, sep, name);
    + }
    +
    if (rc != 0)
    module_put(provider);
    return rc;
    @@ -163,14 +182,19 @@ static void nd_async_device_unregister(void *d, async_cookie_t cookie)
    put_device(dev);
    }

    -void nd_device_register(struct device *dev)
    +void __nd_device_register(struct device *dev)
    {
    dev->bus = &nvdimm_bus_type;
    - device_initialize(dev);
    get_device(dev);
    async_schedule_domain(nd_async_device_register, dev,
    &nd_async_domain);
    }
    +
    +void nd_device_register(struct device *dev)
    +{
    + device_initialize(dev);
    + __nd_device_register(dev);
    +}
    EXPORT_SYMBOL(nd_device_register);

    void nd_device_unregister(struct device *dev, enum nd_async_mode mode)
    @@ -219,6 +243,60 @@ int __nd_driver_register(struct nd_device_driver *nd_drv, struct module *owner,
    }
    EXPORT_SYMBOL(__nd_driver_register);

    +/**
    + * nvdimm_bus_add_disk() - attach and run actions on an nvdimm block device
    + * @disk: disk device being registered
    + *
    + * Note, that @disk must be a descendant of an nvdimm_bus
    + */
    +int nvdimm_bus_add_disk(struct gendisk *disk)
    +{
    + const struct block_device_operations *ops = disk->fops;
    + struct device *dev = disk->driverfs_dev;
    + struct nvdimm_bus *nvdimm_bus;
    +
    + nvdimm_bus = walk_to_nvdimm_bus(dev);
    + if (!nvdimm_bus || !ops->rw_bytes)
    + return -EINVAL;
    +
    + /*
    + * Take the bus lock here to prevent userspace racing to
    + * initiate actions on the newly availble block device while
    + * autodetect scanning is still in flight.
    + */
    + nvdimm_bus_lock(&nvdimm_bus->dev);
    + add_disk(disk);
    + nd_btt_add_disk(nvdimm_bus, disk);
    + nvdimm_bus_unlock(&nvdimm_bus->dev);
    +
    + return 0;
    +}
    +EXPORT_SYMBOL(nvdimm_bus_add_disk);
    +
    +void nvdimm_bus_remove_disk(struct gendisk *disk)
    +{
    + struct device *dev = disk_to_dev(disk);
    + struct nvdimm_bus *nvdimm_bus;
    +
    + nvdimm_bus = walk_to_nvdimm_bus(dev);
    + if (!nvdimm_bus)
    + return;
    +
    + nvdimm_bus_lock(&nvdimm_bus->dev);
    + nd_btt_remove_disk(nvdimm_bus, disk);
    + nvdimm_bus_unlock(&nvdimm_bus->dev);
    +
    + /*
    + * Flush in case *_notify_remove() kicked off asynchronous
    + * device unregistration
    + */
    + nd_synchronize();
    +
    + del_gendisk(disk);
    + put_disk(disk);
    +}
    +EXPORT_SYMBOL(nvdimm_bus_remove_disk);
    +
    static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
    char *buf)
    {
    diff --git a/drivers/nvdimm/core.c b/drivers/nvdimm/core.c
    index dd824d7c2669..0fa9b6225450 100644
    --- a/drivers/nvdimm/core.c
    +++ b/drivers/nvdimm/core.c
    @@ -273,10 +273,28 @@ static ssize_t wait_probe_show(struct device *dev,
    }
    static DEVICE_ATTR_RO(wait_probe);

    +static ssize_t btt_seed_show(struct device *dev,
    + struct device_attribute *attr, char *buf)
    +{
    + struct nvdimm_bus *nvdimm_bus = to_nvdimm_bus(dev);
    + ssize_t rc;
    +
    + nvdimm_bus_lock(dev);
    + if (nvdimm_bus->nd_btt)
    + rc = sprintf(buf, "%s\n", dev_name(&nvdimm_bus->nd_btt->dev));
    + else
    + rc = sprintf(buf, "\n");
    + nvdimm_bus_unlock(dev);
    +
    + return rc;
    +}
    +static DEVICE_ATTR_RO(btt_seed);
    +
    static struct attribute *nvdimm_bus_attributes[] = {
    &dev_attr_commands.attr,
    &dev_attr_wait_probe.attr,
    &dev_attr_provider.attr,
    + &dev_attr_btt_seed.attr,
    NULL,
    };

    @@ -322,6 +340,8 @@ struct nvdimm_bus *__nvdimm_bus_register(struct device *parent,
    list_add_tail(&nvdimm_bus->list, &nvdimm_bus_list);
    mutex_unlock(&nvdimm_bus_list_mutex);

    + nvdimm_bus->nd_btt = nd_btt_create(nvdimm_bus);
    +
    return nvdimm_bus;
    err:
    put_device(&nvdimm_bus->dev);
    diff --git a/drivers/nvdimm/nd-core.h b/drivers/nvdimm/nd-core.h
    index 78d6c51f4bac..1375d30b3da5 100644
    --- a/drivers/nvdimm/nd-core.h
    +++ b/drivers/nvdimm/nd-core.h
    @@ -23,6 +23,11 @@ extern struct list_head nvdimm_bus_list;
    extern struct mutex nvdimm_bus_list_mutex;
    extern int nvdimm_major;

    +struct block_device;
    +struct nd_io_claim;
    +struct nd_btt;
    +struct nd_io;
    +
    struct nvdimm_bus {
    struct nvdimm_bus_descriptor *nd_desc;
    wait_queue_head_t probe_wait;
    @@ -31,6 +36,7 @@ struct nvdimm_bus {
    struct device dev;
    int id, probe_active;
    struct mutex reconfig_mutex;
    + struct nd_btt *nd_btt;
    };

    struct nvdimm {
    @@ -45,6 +51,33 @@ struct nvdimm {
    bool is_nvdimm(struct device *dev);
    bool is_nd_blk(struct device *dev);
    bool is_nd_pmem(struct device *dev);
    +struct gendisk;
    +#if IS_ENABLED(CONFIG_ND_BTT_DEVS)
    +bool is_nd_btt(struct device *dev);
    +struct nd_btt *nd_btt_create(struct nvdimm_bus *nvdimm_bus);
    +void nd_btt_add_disk(struct nvdimm_bus *nvdimm_bus, struct gendisk *disk);
    +void nd_btt_remove_disk(struct nvdimm_bus *nvdimm_bus, struct gendisk *disk);
    +#else
    +static inline bool is_nd_btt(struct device *dev)
    +{
    + return false;
    +}
    +
    +static inline struct nd_btt *nd_btt_create(struct nvdimm_bus *nvdimm_bus)
    +{
    + return NULL;
    +}
    +
    +static inline void nd_btt_add_disk(struct nvdimm_bus *nvdimm_bus,
    + struct gendisk *disk)
    +{
    +}
    +
    +static inline void nd_btt_remove_disk(struct nvdimm_bus *nvdimm_bus,
    + struct gendisk *disk)
    +{
    +}
    +#endif
    struct nvdimm_bus *walk_to_nvdimm_bus(struct device *nd_dev);
    int __init nvdimm_bus_init(void);
    void nvdimm_bus_exit(void);
    @@ -58,6 +91,7 @@ void nd_synchronize(void);
    int nvdimm_bus_register_dimms(struct nvdimm_bus *nvdimm_bus);
    int nvdimm_bus_register_regions(struct nvdimm_bus *nvdimm_bus);
    int nvdimm_bus_init_interleave_sets(struct nvdimm_bus *nvdimm_bus);
    +void __nd_device_register(struct device *dev);
    int nd_match_dimm(struct device *dev, void *data);
    struct nd_label_id;
    char *nd_label_gen_id(struct nd_label_id *label_id, u8 *uuid, u32 flags);
    diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
    index bfa849617358..3bd8d650340e 100644
    --- a/drivers/nvdimm/nd.h
    +++ b/drivers/nvdimm/nd.h
    @@ -14,11 +14,17 @@
    #define __ND_H__
    #include <linux/libnvdimm.h>
    #include <linux/device.h>
    +#include <linux/genhd.h>
    #include <linux/mutex.h>
    #include <linux/ndctl.h>
    #include <linux/types.h>
    +#include <linux/fs.h>
    #include "label.h"

    +enum {
    + SECTOR_SHIFT = 9,
    +};
    +
    struct nvdimm_drvdata {
    struct device *dev;
    int nsindex_size;
    @@ -94,6 +100,14 @@ static inline unsigned nd_inc_seq(unsigned seq)
    return next[seq & 3];
    }

    +struct nd_btt {
    + struct device dev;
    + struct block_device *backing_dev;
    + unsigned long lbasize;
    + u8 *uuid;
    + int id;
    +};
    +
    enum nd_async_mode {
    ND_SYNC,
    ND_ASYNC,
    @@ -118,6 +132,9 @@ int nvdimm_init_nsarea(struct nvdimm_drvdata *ndd);
    int nvdimm_init_config_data(struct nvdimm_drvdata *ndd);
    int nvdimm_set_config_data(struct nvdimm_drvdata *ndd, size_t offset,
    void *buf, size_t len);
    +struct nd_btt *to_nd_btt(struct device *dev);
    +struct btt_sb;
    +u64 nd_btt_sb_checksum(struct btt_sb *btt_sb);
    struct nd_region *to_nd_region(struct device *dev);
    int nd_region_to_nstype(struct nd_region *nd_region);
    int nd_region_register_namespaces(struct nd_region *nd_region, int *err);
    @@ -125,6 +142,8 @@ u64 nd_region_interleave_set_cookie(struct nd_region *nd_region);
    void nvdimm_bus_lock(struct device *dev);
    void nvdimm_bus_unlock(struct device *dev);
    bool is_nvdimm_bus_locked(struct device *dev);
    +int nvdimm_bus_add_disk(struct gendisk *disk);
    +void nvdimm_bus_remove_disk(struct gendisk *disk);
    void nvdimm_drvdata_release(struct kref *kref);
    void put_ndd(struct nvdimm_drvdata *ndd);
    int nd_label_reserve_dpa(struct nvdimm_drvdata *ndd);
    diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
    index efa2cde7f6b6..1f4767150975 100644
    --- a/drivers/nvdimm/pmem.c
    +++ b/drivers/nvdimm/pmem.c
    @@ -190,8 +190,6 @@ static struct pmem_device *pmem_alloc(struct device *dev,
    set_capacity(disk, pmem->size >> 9);
    pmem->pmem_disk = disk;

    - add_disk(disk);
    -
    return pmem;

    out_free_queue:
    @@ -208,8 +206,7 @@ out:

    static void pmem_free(struct pmem_device *pmem)
    {
    - del_gendisk(pmem->pmem_disk);
    - put_disk(pmem->pmem_disk);
    + nvdimm_bus_remove_disk(pmem->pmem_disk);
    blk_cleanup_queue(pmem->pmem_queue);
    iounmap(pmem->virt_addr);
    release_mem_region(pmem->phys_addr, pmem->size);
    @@ -244,6 +241,7 @@ static int nd_pmem_probe(struct device *dev)
    return PTR_ERR(pmem);

    dev_set_drvdata(dev, pmem);
    + nvdimm_bus_add_disk(pmem->pmem_disk);

    return 0;
    }
    diff --git a/include/uapi/linux/ndctl.h b/include/uapi/linux/ndctl.h
    index 2b94ea2287bb..4c2e3ff374b2 100644
    --- a/include/uapi/linux/ndctl.h
    +++ b/include/uapi/linux/ndctl.h
    @@ -181,6 +181,7 @@ static inline const char *nvdimm_cmd_name(unsigned cmd)
    #define ND_DEVICE_NAMESPACE_IO 4 /* legacy persistent memory */
    #define ND_DEVICE_NAMESPACE_PMEM 5 /* PMEM namespace (may alias with BLK) */
    #define ND_DEVICE_NAMESPACE_BLK 6 /* BLK namespace (may alias with PMEM) */
    +#define ND_DEVICE_BTT 7 /* block-translation table device */

    enum nd_driver_flags {
    ND_DRIVER_DIMM = 1 << ND_DEVICE_DIMM,
    @@ -189,6 +190,7 @@ enum nd_driver_flags {
    ND_DRIVER_NAMESPACE_IO = 1 << ND_DEVICE_NAMESPACE_IO,
    ND_DRIVER_NAMESPACE_PMEM = 1 << ND_DEVICE_NAMESPACE_PMEM,
    ND_DRIVER_NAMESPACE_BLK = 1 << ND_DEVICE_NAMESPACE_BLK,
    + ND_DRIVER_BTT = 1 << ND_DEVICE_BTT,
    };

    enum {


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