Re: [PATCH v2 1/3] /dev/dax, pmem: direct access to persistent memory

From: Johannes Thumshirn <jthumshirn@suse.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-nvdimm@lists.01.org,
	Dave Hansen <dave.hansen@linux.intel.com>,
	linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	hch@lst.de
Subject: Re: [PATCH v2 1/3] /dev/dax, pmem: direct access to persistent memory
Date: Tue, 17 May 2016 10:52:00 +0200	[thread overview]
Message-ID: <20160517085200.GH17154@c203.arch.suse.de> (raw)
In-Reply-To: <146329358394.17948.9595519335631675126.stgit@dwillia2-desk3.amr.corp.intel.com>

On Sat, May 14, 2016 at 11:26:24PM -0700, Dan Williams wrote:
> Device DAX is the device-centric analogue of Filesystem DAX
> (CONFIG_FS_DAX).  It allows memory ranges to be allocated and mapped
> without need of an intervening file system.  Device DAX is strict,
> precise and predictable.  Specifically this interface:
> 
> 1/ Guarantees fault granularity with respect to a given page size (pte,
> pmd, or pud) set at configuration time.
> 
> 2/ Enforces deterministic behavior by being strict about what fault
> scenarios are supported.
> 
> For example, by forcing MADV_DONTFORK semantics and omitting MAP_PRIVATE
> support device-dax guarantees that a mapping always behaves/performs the
> same once established.  It is the "what you see is what you get" access
> mechanism to differentiated memory vs filesystem DAX which has
> filesystem specific implementation semantics.
> 
> Persistent memory is the first target, but the mechanism is also
> targeted for exclusive allocations of performance differentiated memory
> ranges.
> 
> This commit is limited to the base device driver infrastructure to
> associate a dax device with pmem range.
> 
> Cc: Jeff Moyer <jmoyer@redhat.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/Kconfig                     |    2 
>  drivers/Makefile                    |    1 
>  drivers/dax/Kconfig                 |   25 +++
>  drivers/dax/Makefile                |    4 +
>  drivers/dax/dax.c                   |  252 +++++++++++++++++++++++++++++++++++
>  drivers/dax/dax.h                   |   24 +++
>  drivers/dax/pmem.c                  |  168 +++++++++++++++++++++++

Is a DAX device always a NVDIMM device, or can it be something else (like the
S390 dcssblk)? If it's NVDIMM only I'd suggest it to go under the
drivers/nvdimm directory.

>  tools/testing/nvdimm/Kbuild         |    9 +
>  tools/testing/nvdimm/config_check.c |    2 
>  9 files changed, 487 insertions(+)
>  create mode 100644 drivers/dax/Kconfig
>  create mode 100644 drivers/dax/Makefile
>  create mode 100644 drivers/dax/dax.c
>  create mode 100644 drivers/dax/dax.h
>  create mode 100644 drivers/dax/pmem.c
> 
> diff --git a/drivers/Kconfig b/drivers/Kconfig
> index d2ac339de85f..8298eab84a6f 100644
> --- a/drivers/Kconfig
> +++ b/drivers/Kconfig
> @@ -190,6 +190,8 @@ source "drivers/android/Kconfig"
>  
>  source "drivers/nvdimm/Kconfig"
>  
> +source "drivers/dax/Kconfig"
> +
>  source "drivers/nvmem/Kconfig"
>  
>  source "drivers/hwtracing/stm/Kconfig"
> diff --git a/drivers/Makefile b/drivers/Makefile
> index 8f5d076baeb0..0b6f3d60193d 100644
> --- a/drivers/Makefile
> +++ b/drivers/Makefile
> @@ -66,6 +66,7 @@ obj-$(CONFIG_PARPORT)		+= parport/
>  obj-$(CONFIG_NVM)		+= lightnvm/
>  obj-y				+= base/ block/ misc/ mfd/ nfc/
>  obj-$(CONFIG_LIBNVDIMM)		+= nvdimm/
> +obj-$(CONFIG_DEV_DAX)		+= dax/
>  obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf/
>  obj-$(CONFIG_NUBUS)		+= nubus/
>  obj-y				+= macintosh/
> diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
> new file mode 100644
> index 000000000000..86ffbaa891ad
> --- /dev/null
> +++ b/drivers/dax/Kconfig
> @@ -0,0 +1,25 @@
> +menuconfig DEV_DAX
> +	tristate "DAX: direct access to differentiated memory"
> +	default m if NVDIMM_DAX
> +	help
> +	  Support raw access to differentiated (persistence, bandwidth,
> +	  latency...) memory via an mmap(2) capable character
> +	  device.  Platform firmware or a device driver may identify a
> +	  platform memory resource that is differentiated from the
> +	  baseline memory pool.  Mappings of a /dev/daxX.Y device impose
> +	  restrictions that make the mapping behavior deterministic.
> +
> +if DEV_DAX
> +
> +config DEV_DAX_PMEM
> +	tristate "PMEM DAX: direct access to persistent memory"
> +	depends on NVDIMM_DAX
> +	default DEV_DAX
> +	help
> +	  Support raw access to persistent memory.  Note that this
> +	  driver consumes memory ranges allocated and exported by the
> +	  libnvdimm sub-system.
> +
> +	  Say Y if unsure
> +
> +endif
> diff --git a/drivers/dax/Makefile b/drivers/dax/Makefile
> new file mode 100644
> index 000000000000..27c54e38478a
> --- /dev/null
> +++ b/drivers/dax/Makefile
> @@ -0,0 +1,4 @@
> +obj-$(CONFIG_DEV_DAX) += dax.o
> +obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem.o
> +
> +dax_pmem-y := pmem.o
> diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
> new file mode 100644
> index 000000000000..8207fb33a992
> --- /dev/null
> +++ b/drivers/dax/dax.c
> @@ -0,0 +1,252 @@
> +/*
> + * Copyright(c) 2016 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/pagemap.h>
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/pfn_t.h>
> +#include <linux/slab.h>
> +#include <linux/dax.h>
> +#include <linux/fs.h>
> +#include <linux/mm.h>
> +
> +static int dax_major;
> +static struct class *dax_class;
> +static DEFINE_IDA(dax_minor_ida);
> +
> +/**
> + * struct dax_region - mapping infrastructure for dax devices
> + * @id: kernel-wide unique region for a memory range
> + * @base: linear address corresponding to @res
> + * @kref: to pin while other agents have a need to do lookups
> + * @dev: parent device backing this region
> + * @align: allocation and mapping alignment for child dax devices
> + * @res: physical address range of the region
> + * @pfn_flags: identify whether the pfns are paged back or not
> + */
> +struct dax_region {
> +	int id;
> +	struct ida ida;
> +	void *base;
> +	struct kref kref;
> +	struct device *dev;
> +	unsigned int align;
> +	struct resource res;
> +	unsigned long pfn_flags;
> +};
> +
> +/**
> + * struct dax_dev - subdivision of a dax region
> + * @region - parent region
> + * @dev - device backing the character device
> + * @kref - enable this data to be tracked in filp->private_data
> + * @id - child id in the region
> + * @num_resources - number of physical address extents in this device
> + * @res - array of physical address ranges
> + */
> +struct dax_dev {
> +	struct dax_region *region;
> +	struct device *dev;
> +	struct kref kref;
> +	int id;
> +	int num_resources;
> +	struct resource res[0];
> +};
> +
> +static void dax_region_free(struct kref *kref)
> +{
> +	struct dax_region *dax_region;
> +
> +	dax_region = container_of(kref, struct dax_region, kref);
> +	kfree(dax_region);
> +}
> +
> +void dax_region_put(struct dax_region *dax_region)
> +{
> +	kref_put(&dax_region->kref, dax_region_free);
> +}
> +EXPORT_SYMBOL_GPL(dax_region_put);

dax_region_get() ??

> +
> +static void dax_dev_free(struct kref *kref)
> +{
> +	struct dax_dev *dax_dev;
> +
> +	dax_dev = container_of(kref, struct dax_dev, kref);
> +	dax_region_put(dax_dev->region);
> +	kfree(dax_dev);
> +}
> +
> +static void dax_dev_put(struct dax_dev *dax_dev)
> +{
> +	kref_put(&dax_dev->kref, dax_dev_free);
> +}
> +
> +struct dax_region *alloc_dax_region(struct device *parent, int region_id,
> +		struct resource *res, unsigned int align, void *addr,
> +		unsigned long pfn_flags)
> +{
> +	struct dax_region *dax_region;
> +
> +	dax_region = kzalloc(sizeof(*dax_region), GFP_KERNEL);
> +
> +	if (!dax_region)
> +		return NULL;
> +
> +	memcpy(&dax_region->res, res, sizeof(*res));
> +	dax_region->pfn_flags = pfn_flags;
> +	kref_init(&dax_region->kref);
> +	dax_region->id = region_id;
> +	ida_init(&dax_region->ida);
> +	dax_region->align = align;
> +	dax_region->dev = parent;
> +	dax_region->base = addr;
> +
> +	return dax_region;
> +}
> +EXPORT_SYMBOL_GPL(alloc_dax_region);
> +
> +static ssize_t size_show(struct device *dev,
> +		struct device_attribute *attr, char *buf)
> +{
> +	struct dax_dev *dax_dev = dev_get_drvdata(dev);
> +	unsigned long long size = 0;
> +	int i;
> +
> +	for (i = 0; i < dax_dev->num_resources; i++)
> +		size += resource_size(&dax_dev->res[i]);
> +
> +	return sprintf(buf, "%llu\n", size);
> +}
> +static DEVICE_ATTR_RO(size);
> +
> +static struct attribute *dax_device_attributes[] = {
> +	&dev_attr_size.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group dax_device_attribute_group = {
> +	.attrs = dax_device_attributes,
> +};
> +
> +static const struct attribute_group *dax_attribute_groups[] = {
> +	&dax_device_attribute_group,
> +	NULL,
> +};
> +
> +static void destroy_dax_dev(void *_dev)
> +{
> +	struct device *dev = _dev;
> +	struct dax_dev *dax_dev = dev_get_drvdata(dev);
> +	struct dax_region *dax_region = dax_dev->region;
> +
> +	dev_dbg(dev, "%s\n", __func__);

This dev_dbg() could be replaced by function graph tracing.

> +
> +	get_device(dev);
> +	device_unregister(dev);
> +	ida_simple_remove(&dax_region->ida, dax_dev->id);
> +	ida_simple_remove(&dax_minor_ida, MINOR(dev->devt));
> +	put_device(dev);
> +	dax_dev_put(dax_dev);
> +}
> +
> +int devm_create_dax_dev(struct dax_region *dax_region, struct resource *res,
> +		int count)
> +{
> +	struct device *parent = dax_region->dev;
> +	struct dax_dev *dax_dev;
> +	struct device *dev;
> +	int rc, minor;
> +	dev_t dev_t;
> +
> +	dax_dev = kzalloc(sizeof(*dax_dev) + sizeof(*res) * count, GFP_KERNEL);
> +	if (!dax_dev)
> +		return -ENOMEM;
> +	memcpy(dax_dev->res, res, sizeof(*res) * count);
> +	dax_dev->num_resources = count;
> +	kref_init(&dax_dev->kref);
> +	dax_dev->region = dax_region;
> +	kref_get(&dax_region->kref);

dax_region_get() ?

> +
> +	dax_dev->id = ida_simple_get(&dax_region->ida, 0, 0, GFP_KERNEL);
> +	if (dax_dev->id < 0) {
> +		rc = dax_dev->id;
> +		goto err_id;
> +	}
> +
> +	minor = ida_simple_get(&dax_minor_ida, 0, 0, GFP_KERNEL);
> +	if (minor < 0) {
> +		rc = minor;
> +		goto err_minor;
> +	}
> +
> +	dev_t = MKDEV(dax_major, minor);
> +	dev = device_create_with_groups(dax_class, parent, dev_t, dax_dev,
> +			dax_attribute_groups, "dax%d.%d", dax_region->id,
> +			dax_dev->id);
> +	if (IS_ERR(dev)) {
> +		rc = PTR_ERR(dev);
> +		goto err_create;
> +	}
> +	dax_dev->dev = dev;
> +
> +	rc = devm_add_action(dax_region->dev, destroy_dax_dev, dev);
> +	if (rc) {
> +		destroy_dax_dev(dev);
> +		return rc;
> +	}
> +
> +	return 0;
> +
> + err_create:
> +	ida_simple_remove(&dax_minor_ida, minor);
> + err_minor:
> +	ida_simple_remove(&dax_region->ida, dax_dev->id);
> + err_id:
> +	dax_dev_put(dax_dev);
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(devm_create_dax_dev);
> +
> +static const struct file_operations dax_fops = {
> +	.llseek = noop_llseek,
> +	.owner = THIS_MODULE,
> +};
> +
> +static int __init dax_init(void)
> +{
> +	int rc;
> +
> +	rc = register_chrdev(0, "dax", &dax_fops);
> +	if (rc < 0)
> +		return rc;
> +	dax_major = rc;
> +
> +	dax_class = class_create(THIS_MODULE, "dax");
> +	if (IS_ERR(dax_class)) {
> +		unregister_chrdev(dax_major, "dax");
> +		return PTR_ERR(dax_class);
> +	}
> +
> +	return 0;
> +}
> +
> +static void __exit dax_exit(void)
> +{
> +	class_destroy(dax_class);
> +	unregister_chrdev(dax_major, "dax");

AFAICT you're missing a call to ida_destroy(&dax_minor_ida); here.

> +}
> +
> +MODULE_AUTHOR("Intel Corporation");
> +MODULE_LICENSE("GPL v2");
> +subsys_initcall(dax_init);
> +module_exit(dax_exit);
> diff --git a/drivers/dax/dax.h b/drivers/dax/dax.h
> new file mode 100644
> index 000000000000..d8b8f1f25054
> --- /dev/null
> +++ b/drivers/dax/dax.h
> @@ -0,0 +1,24 @@
> +/*
> + * Copyright(c) 2016 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.
> + */
> +#ifndef __DAX_H__
> +#define __DAX_H__
> +struct device;
> +struct resource;
> +struct dax_region;
> +void dax_region_put(struct dax_region *dax_region);
> +struct dax_region *alloc_dax_region(struct device *parent,
> +		int region_id, struct resource *res, unsigned int align,
> +		void *addr, unsigned long flags);
> +int devm_create_dax_dev(struct dax_region *dax_region, struct resource *res,
> +		int count);
> +#endif /* __DAX_H__ */
> diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
> new file mode 100644
> index 000000000000..4e97555e1cab
> --- /dev/null
> +++ b/drivers/dax/pmem.c
> @@ -0,0 +1,168 @@
> +/*
> + * Copyright(c) 2016 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/percpu-refcount.h>
> +#include <linux/memremap.h>
> +#include <linux/module.h>
> +#include <linux/pfn_t.h>
> +#include "../nvdimm/pfn.h"
> +#include "../nvdimm/nd.h"
> +#include "dax.h"
> +
> +struct dax_pmem {
> +	struct device *dev;
> +	struct percpu_ref ref;
> +	struct completion cmp;
> +};
> +
> +struct dax_pmem *to_dax_pmem(struct percpu_ref *ref)
> +{
> +	return container_of(ref, struct dax_pmem, ref);
> +}
> +
> +static void dax_pmem_percpu_release(struct percpu_ref *ref)
> +{
> +	struct dax_pmem *dax_pmem = to_dax_pmem(ref);
> +
> +	dev_dbg(dax_pmem->dev, "%s\n", __func__);

This dev_dbg() could be replaced by function graph tracing.

> +	complete(&dax_pmem->cmp);
> +}
> +
> +static void dax_pmem_percpu_exit(void *data)
> +{
> +	struct percpu_ref *ref = data;
> +	struct dax_pmem *dax_pmem = to_dax_pmem(ref);
> +
> +	dev_dbg(dax_pmem->dev, "%s\n", __func__);

Same as above.

> +	percpu_ref_exit(ref);
> +	wait_for_completion(&dax_pmem->cmp);
> +}
> +
> +static void dax_pmem_percpu_kill(void *data)
> +{
> +	struct percpu_ref *ref = data;
> +	struct dax_pmem *dax_pmem = to_dax_pmem(ref);
> +
> +	dev_dbg(dax_pmem->dev, "%s\n", __func__);

Same as above.

> +	percpu_ref_kill(ref);
> +}
> +
> +static int dax_pmem_probe(struct device *dev)
> +{
> +	int rc;
> +	void *addr;
> +	struct resource res;
> +	struct nd_pfn_sb *pfn_sb;
> +	struct dax_pmem *dax_pmem;
> +	struct nd_region *nd_region;
> +	struct nd_namespace_io *nsio;
> +	struct dax_region *dax_region;
> +	struct nd_namespace_common *ndns;
> +	struct nd_dax *nd_dax = to_nd_dax(dev);
> +	struct nd_pfn *nd_pfn = &nd_dax->nd_pfn;
> +	struct vmem_altmap __altmap, *altmap = NULL;
> +
> +	ndns = nvdimm_namespace_common_probe(dev);
> +	if (IS_ERR(ndns))
> +		return PTR_ERR(ndns);
> +	nsio = to_nd_namespace_io(&ndns->dev);
> +
> +	/* parse the 'pfn' info block via ->rw_bytes */
> +	devm_nsio_enable(dev, nsio);
> +	altmap = nvdimm_setup_pfn(nd_pfn, &res, &__altmap);
> +	if (IS_ERR(altmap))
> +		return PTR_ERR(altmap);
> +	devm_nsio_disable(dev, nsio);
> +
> +	pfn_sb = nd_pfn->pfn_sb;
> +
> +	if (!devm_request_mem_region(dev, nsio->res.start,
> +				resource_size(&nsio->res), dev_name(dev))) {
> +		dev_warn(dev, "could not reserve region %pR\n", &nsio->res);
> +		return -EBUSY;
> +	}
> +
> +	dax_pmem = devm_kzalloc(dev, sizeof(*dax_pmem), GFP_KERNEL);
> +	if (!dax_pmem)
> +		return -ENOMEM;
> +
> +	dax_pmem->dev = dev;
> +	init_completion(&dax_pmem->cmp);
> +	rc = percpu_ref_init(&dax_pmem->ref, dax_pmem_percpu_release, 0,
> +			GFP_KERNEL);
> +	if (rc)
> +		return rc;
> +
> +	rc = devm_add_action(dev, dax_pmem_percpu_exit, &dax_pmem->ref);
> +	if (rc) {
> +		dax_pmem_percpu_exit(&dax_pmem->ref);
> +		return rc;
> +	}
> +
> +	addr = devm_memremap_pages(dev, &res, &dax_pmem->ref, altmap);
> +	if (IS_ERR(addr))
> +		return PTR_ERR(addr);
> +
> +	rc = devm_add_action(dev, dax_pmem_percpu_kill, &dax_pmem->ref);
> +	if (rc) {
> +		dax_pmem_percpu_kill(&dax_pmem->ref);
> +		return rc;
> +	}
> +
> +	nd_region = to_nd_region(dev->parent);
> +	dax_region = alloc_dax_region(dev, nd_region->id, &res,
> +			le32_to_cpu(pfn_sb->align), addr, PFN_DEV|PFN_MAP);
> +	if (!dax_region)
> +		return -ENOMEM;
> +
> +	/* TODO: support for subdividing a dax region... */
> +	rc = devm_create_dax_dev(dax_region, &res, 1);
> +
> +	/* child dax_dev instances now own the lifetime of the dax_region */
> +	dax_region_put(dax_region);
> +
> +	return rc;
> +}
> +
> +static int dax_pmem_remove(struct device *dev)
> +{
> +	/*
> +	 * The init path is fully devm-enabled, or child devices
> +	 * otherwise hold references on parent resources.
> +	 */

So remove is completely pointless here. Why are you depending on it in 
__nd_driver_register()? __device_release_driver() does not depend on a remove
callback to be present.

> +	return 0;
> +}
> +
> +static struct nd_device_driver dax_pmem_driver = {
> +	.probe = dax_pmem_probe,
> +	.remove = dax_pmem_remove,
> +	.drv = {
> +		.name = "dax_pmem",
> +	},
> +	.type = ND_DRIVER_DAX_PMEM,
> +};
> +
> +static int __init dax_pmem_init(void)
> +{
> +	return nd_driver_register(&dax_pmem_driver);
> +}
> +module_init(dax_pmem_init);
> +
> +static void __exit dax_pmem_exit(void)
> +{
> +	driver_unregister(&dax_pmem_driver.drv);
> +}
> +module_exit(dax_pmem_exit);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Intel Corporation");
> +MODULE_ALIAS_ND_DEVICE(ND_DEVICE_DAX_PMEM);
> diff --git a/tools/testing/nvdimm/Kbuild b/tools/testing/nvdimm/Kbuild
> index 5ff6d3c126a9..785985677159 100644
> --- a/tools/testing/nvdimm/Kbuild
> +++ b/tools/testing/nvdimm/Kbuild
> @@ -16,6 +16,7 @@ ldflags-y += --wrap=phys_to_pfn_t
>  DRIVERS := ../../../drivers
>  NVDIMM_SRC := $(DRIVERS)/nvdimm
>  ACPI_SRC := $(DRIVERS)/acpi
> +DAX_SRC := $(DRIVERS)/dax
>  
>  obj-$(CONFIG_LIBNVDIMM) += libnvdimm.o
>  obj-$(CONFIG_BLK_DEV_PMEM) += nd_pmem.o
> @@ -23,6 +24,8 @@ obj-$(CONFIG_ND_BTT) += nd_btt.o
>  obj-$(CONFIG_ND_BLK) += nd_blk.o
>  obj-$(CONFIG_X86_PMEM_LEGACY) += nd_e820.o
>  obj-$(CONFIG_ACPI_NFIT) += nfit.o
> +obj-$(CONFIG_DEV_DAX) += dax.o
> +obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem.o
>  
>  nfit-y := $(ACPI_SRC)/nfit.o
>  nfit-y += config_check.o
> @@ -39,6 +42,12 @@ nd_blk-y += config_check.o
>  nd_e820-y := $(NVDIMM_SRC)/e820.o
>  nd_e820-y += config_check.o
>  
> +dax-y := $(DAX_SRC)/dax.o
> +dax-y += config_check.o
> +
> +dax_pmem-y := $(DAX_SRC)/pmem.o
> +dax_pmem-y += config_check.o
> +
>  libnvdimm-y := $(NVDIMM_SRC)/core.o
>  libnvdimm-y += $(NVDIMM_SRC)/bus.o
>  libnvdimm-y += $(NVDIMM_SRC)/dimm_devs.o
> diff --git a/tools/testing/nvdimm/config_check.c b/tools/testing/nvdimm/config_check.c
> index f2c7615554eb..adf18bfeca00 100644
> --- a/tools/testing/nvdimm/config_check.c
> +++ b/tools/testing/nvdimm/config_check.c
> @@ -12,4 +12,6 @@ void check(void)
>  	BUILD_BUG_ON(!IS_MODULE(CONFIG_ND_BTT));
>  	BUILD_BUG_ON(!IS_MODULE(CONFIG_ND_BLK));
>  	BUILD_BUG_ON(!IS_MODULE(CONFIG_ACPI_NFIT));
> +	BUILD_BUG_ON(!IS_MODULE(CONFIG_DEV_DAX));
> +	BUILD_BUG_ON(!IS_MODULE(CONFIG_DEV_DAX_PMEM));
>  }
> 
> _______________________________________________
> Linux-nvdimm mailing list
> Linux-nvdimm@lists.01.org
> https://lists.01.org/mailman/listinfo/linux-nvdimm

-- 
Johannes Thumshirn                                          Storage
jthumshirn@suse.de                                +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)
Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850
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