Commit 730926c3 authored by Dan Williams's avatar Dan Williams
Browse files

device-dax: Add /sys/class/dax backwards compatibility 



On the expectation that some environments may not upgrade libdaxctl
(userspace component that depends on the /sys/class/dax hierarchy),
provide a default / legacy dax_pmem_compat driver. The dax_pmem_compat
driver implements the original /sys/class/dax sysfs layout rather than
/sys/bus/dax. When userspace is upgraded it can blacklist this module
and switch to the dax_pmem driver going forward.

CONFIG_DEV_DAX_PMEM_COMPAT and supporting code will be deleted according
to the dax_pmem entry in Documentation/ABI/obsolete/.

Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent d200781e

Documentation/ABI/obsolete/sysfs-class-dax

0 → 100644
+22 −0
Original line number Diff line number Diff line 
What:           /sys/class/dax/

Date:           May, 2016

KernelVersion:  v4.7

Contact:        linux-nvdimm@lists.01.org

Description:	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.



		The /sys/class/dax/ interface enumerates all the

		device-dax instances in the system. The ABI is

		deprecated and will be removed after 2020. It is

		replaced with the DAX bus interface /sys/bus/dax/ where

		device-dax instances can be found under

		/sys/bus/dax/devices/

drivers/dax/Kconfig

+11 −1
Original line number Diff line number Diff line
@@ -23,12 +23,22 @@ config DEV_DAX 
config DEV_DAX_PMEM

	tristate "PMEM DAX: direct access to persistent memory"

	depends on LIBNVDIMM && NVDIMM_DAX && DEV_DAX

	depends on m # until we can kill DEV_DAX_PMEM_COMPAT

	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

	  Say M if unsure



config DEV_DAX_PMEM_COMPAT

	tristate "PMEM DAX: support the deprecated /sys/class/dax interface"

	depends on DEV_DAX_PMEM

	default DEV_DAX_PMEM

	help

	  Older versions of the libdaxctl library expect to find all

	  device-dax instances under /sys/class/dax. If libdaxctl in

	  your distribution is older than v58 say M, otherwise say N.



endif

drivers/dax/Makefile

+2 −2
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0

obj-$(CONFIG_DAX) += dax.o

obj-$(CONFIG_DEV_DAX) += device_dax.o

obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem.o



dax-y := super.o

dax-y += bus.o

dax_pmem-y := pmem.o

device_dax-y := device.o



obj-y += pmem/

drivers/dax/bus.c

+24 −5
Original line number Diff line number Diff line
@@ -9,6 +9,8 @@ 
#include "dax-private.h"

#include "bus.h"



static struct class *dax_class;



static DEFINE_MUTEX(dax_bus_lock);



#define DAX_NAME_LEN 30
@@ -310,8 +312,8 @@ static void unregister_dev_dax(void *dev) 
	put_device(dev);

}



struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region, int id,

		struct dev_pagemap *pgmap)

struct dev_dax *__devm_create_dev_dax(struct dax_region *dax_region, int id,

		struct dev_pagemap *pgmap, enum dev_dax_subsys subsys)

{

	struct device *parent = dax_region->dev;

	struct dax_device *dax_dev;
@@ -350,7 +352,10 @@ struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region, int id, 


	inode = dax_inode(dax_dev);

	dev->devt = inode->i_rdev;

	if (subsys == DEV_DAX_BUS)

		dev->bus = &dax_bus_type;

	else

		dev->class = dax_class;

	dev->parent = parent;

	dev->groups = dax_attribute_groups;

	dev->release = dev_dax_release;
@@ -374,7 +379,7 @@ struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region, int id, 


	return ERR_PTR(rc);

}

EXPORT_SYMBOL_GPL(devm_create_dev_dax);

EXPORT_SYMBOL_GPL(__devm_create_dev_dax);



static int match_always_count;
@@ -407,6 +412,7 @@ 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);
@@ -416,15 +422,28 @@ void dax_driver_unregister(struct dax_device_driver *dax_drv) 
		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);

	int rc;



	if (IS_ENABLED(CONFIG_DEV_DAX_PMEM_COMPAT)) {

		dax_class = class_create(THIS_MODULE, "dax");

		if (IS_ERR(dax_class))

			return PTR_ERR(dax_class);

	}



	rc = bus_register(&dax_bus_type);

	if (rc)

		class_destroy(dax_class);

	return rc;

}



void __exit dax_bus_exit(void)

{

	bus_unregister(&dax_bus_type);

	class_destroy(dax_class);

}

drivers/dax/bus.h

+23 −3
Original line number Diff line number Diff line
@@ -2,7 +2,8 @@ 
/* Copyright(c) 2016 - 2018 Intel Corporation. All rights reserved. */

#ifndef __DAX_BUS_H__

#define __DAX_BUS_H__

struct device;

#include <linux/device.h>



struct dev_dax;

struct resource;

struct dax_device;
@@ -10,8 +11,23 @@ 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, unsigned long flags);

struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region, int id,

		struct dev_pagemap *pgmap);



enum dev_dax_subsys {

	DEV_DAX_BUS,

	DEV_DAX_CLASS,

};



struct dev_dax *__devm_create_dev_dax(struct dax_region *dax_region, int id,

		struct dev_pagemap *pgmap, enum dev_dax_subsys subsys);



static inline struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,

		int id, struct dev_pagemap *pgmap)

{

	return __devm_create_dev_dax(dax_region, id, pgmap, DEV_DAX_BUS);

}



/* to be deleted when DEV_DAX_CLASS is removed */

struct dev_dax *__dax_pmem_probe(struct device *dev, enum dev_dax_subsys subsys);



struct dax_device_driver {

	struct device_driver drv;
@@ -26,6 +42,10 @@ int __dax_driver_register(struct dax_device_driver *dax_drv, 
void dax_driver_unregister(struct dax_device_driver *dax_drv);

void kill_dev_dax(struct dev_dax *dev_dax);



#if IS_ENABLED(CONFIG_DEV_DAX_PMEM_COMPAT)

int dev_dax_probe(struct device *dev);

#endif



/*

 * While run_dax() is potentially a generic operation that could be

 * defined in include/linux/dax.h we don't want to grow any users

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