[PATCH 8/8] device-dax: Add /sys/class/dax backwards compatibility

From: Dan Williams
Date: Tue Oct 30 2018 - 23:25:24 EST

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: Dan Williams <dan.j.williams@xxxxxxxxx>
---
Documentation/ABI/obsolete/sysfs-class-dax | 22 +++++++
drivers/dax/Kconfig | 12 +++-
drivers/dax/Makefile | 4 +
drivers/dax/bus.c | 29 +++++++--
drivers/dax/bus.h | 26 +++++++-
drivers/dax/device.c | 9 ++-
drivers/dax/pmem.c | 90 ----------------------------
drivers/dax/pmem/Makefile | 7 ++
drivers/dax/pmem/compat.c | 73 +++++++++++++++++++++++
drivers/dax/pmem/core.c | 69 +++++++++++++++++++++
drivers/dax/pmem/pmem.c | 40 ++++++++++++
tools/testing/nvdimm/Kbuild | 6 ++
12 files changed, 283 insertions(+), 104 deletions(-)
create mode 100644 Documentation/ABI/obsolete/sysfs-class-dax
delete mode 100644 drivers/dax/pmem.c
create mode 100644 drivers/dax/pmem/Makefile
create mode 100644 drivers/dax/pmem/compat.c
create mode 100644 drivers/dax/pmem/core.c
create mode 100644 drivers/dax/pmem/pmem.c

diff --git a/Documentation/ABI/obsolete/sysfs-class-dax b/Documentation/ABI/obsolete/sysfs-class-dax
new file mode 100644
index 000000000000..2cb9fc5e8bd1
--- /dev/null
+++ b/Documentation/ABI/obsolete/sysfs-class-dax
@@ -0,0 +1,22 @@
+What: /sys/class/dax/
+Date: May, 2016
+KernelVersion: v4.7
+Contact: linux-nvdimm@xxxxxxxxxxxx
+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/
diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index e0700bf4893a..6fc96f03920e 100644
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -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
diff --git a/drivers/dax/Makefile b/drivers/dax/Makefile
index 658e6b9b1d74..233bbffccbe6 100644
--- a/drivers/dax/Makefile
+++ b/drivers/dax/Makefile
@@ -1,9 +1,9 @@
# 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/
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 178d76504f79..ebf9a4726f6c 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -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;
- dev->bus = &dax_bus_type;
+ 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);
}
diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
index 395ab812367c..ce977552ffb5 100644
--- a/drivers/dax/bus.h
+++ b/drivers/dax/bus.h
@@ -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
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 052aed3ab600..71694cd984a3 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -445,7 +445,7 @@ static void dev_dax_kill(void *dev_dax)
kill_dev_dax(dev_dax);
}

-static int dev_dax_probe(struct device *dev)
+int dev_dax_probe(struct device *dev)
{
struct dev_dax *dev_dax = to_dev_dax(dev);
struct dax_device *dax_dev = dev_dax->dax_dev;
@@ -488,7 +488,11 @@ static int dev_dax_probe(struct device *dev)
inode = dax_inode(dax_dev);
cdev = inode->i_cdev;
cdev_init(cdev, &dax_fops);
- cdev->owner = dev->driver->owner;
+ if (dev->class) {
+ /* for the CONFIG_DEV_DAX_PMEM_COMPAT case */
+ cdev->owner = dev->parent->driver->owner;
+ } else
+ cdev->owner = dev->driver->owner;
cdev_set_parent(cdev, &dev->kobj);
rc = cdev_add(cdev, dev->devt, 1);
if (rc)
@@ -501,6 +505,7 @@ static int dev_dax_probe(struct device *dev)
run_dax(dax_dev);
return devm_add_action_or_reset(dev, dev_dax_kill, dev_dax);
}
+EXPORT_SYMBOL_GPL(dev_dax_probe);

static int dev_dax_remove(struct device *dev)
{
diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
deleted file mode 100644
index d3cefa7868ac..000000000000
--- a/drivers/dax/pmem.c
+++ /dev/null
@@ -1,90 +0,0 @@
-/*
- * 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 "bus.h"
-
-static int dax_pmem_probe(struct device *dev)
-{
- struct resource res;
- int rc, id, region_id;
- resource_size_t offset;
- struct nd_pfn_sb *pfn_sb;
- struct dev_dax *dev_dax;
- struct nd_namespace_io *nsio;
- struct dax_region *dax_region;
- struct dev_pagemap pgmap = { 0 };
- struct nd_namespace_common *ndns;
- struct nd_dax *nd_dax = to_nd_dax(dev);
- struct nd_pfn *nd_pfn = &nd_dax->nd_pfn;
-
- 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 */
- rc = devm_nsio_enable(dev, nsio);
- if (rc)
- return rc;
- rc = nvdimm_setup_pfn(nd_pfn, &pgmap);
- if (rc)
- return rc;
- devm_nsio_disable(dev, nsio);
-
- /* reserve the metadata area, device-dax will reserve the data */
- pfn_sb = nd_pfn->pfn_sb;
- offset = le64_to_cpu(pfn_sb->dataoff);
- if (!devm_request_mem_region(dev, nsio->res.start, offset,
- dev_name(&ndns->dev))) {
- dev_warn(dev, "could not reserve metadata\n");
- return -EBUSY;
- }
-
- rc = sscanf(dev_name(&ndns->dev), "namespace%d.%d", &region_id, &id);
- if (rc != 2)
- return -EINVAL;
-
- /* adjust the dax_region resource to the start of data */
- memcpy(&res, &pgmap.res, sizeof(res));
- res.start += offset;
- dax_region = alloc_dax_region(dev, region_id, &res,
- le32_to_cpu(pfn_sb->align), PFN_DEV|PFN_MAP);
- if (!dax_region)
- return -ENOMEM;
-
- dev_dax = devm_create_dev_dax(dax_region, id, &pgmap);
-
- /* child dev_dax instances now own the lifetime of the dax_region */
- dax_region_put(dax_region);
-
- return PTR_ERR_OR_ZERO(dev_dax);
-}
-
-static struct nd_device_driver dax_pmem_driver = {
- .probe = dax_pmem_probe,
- .drv = {
- .name = "dax_pmem",
- },
- .type = ND_DRIVER_DAX_PMEM,
-};
-
-module_nd_driver(dax_pmem_driver);
-
-MODULE_LICENSE("GPL v2");
-MODULE_AUTHOR("Intel Corporation");
-MODULE_ALIAS_ND_DEVICE(ND_DEVICE_DAX_PMEM);
diff --git a/drivers/dax/pmem/Makefile b/drivers/dax/pmem/Makefile
new file mode 100644
index 000000000000..e2e79bd3fdcf
--- /dev/null
+++ b/drivers/dax/pmem/Makefile
@@ -0,0 +1,7 @@
+obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem.o
+obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem_core.o
+obj-$(CONFIG_DEV_DAX_PMEM_COMPAT) += dax_pmem_compat.o
+
+dax_pmem-y := pmem.o
+dax_pmem_core-y := core.o
+dax_pmem_compat-y := compat.o
diff --git a/drivers/dax/pmem/compat.c b/drivers/dax/pmem/compat.c
new file mode 100644
index 000000000000..d7b15e6f30c5
--- /dev/null
+++ b/drivers/dax/pmem/compat.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016 - 2018 Intel Corporation. All rights reserved. */
+#include <linux/percpu-refcount.h>
+#include <linux/memremap.h>
+#include <linux/module.h>
+#include <linux/pfn_t.h>
+#include <linux/nd.h>
+#include "../bus.h"
+
+/* we need the private definitions to implement compat suport */
+#include "../dax-private.h"
+
+static int dax_pmem_compat_probe(struct device *dev)
+{
+ struct dev_dax *dev_dax = __dax_pmem_probe(dev, DEV_DAX_CLASS);
+ int rc;
+
+ if (IS_ERR(dev_dax))
+ return PTR_ERR(dev_dax);
+
+ if (!devres_open_group(&dev_dax->dev, dev_dax, GFP_KERNEL))
+ return -ENOMEM;
+
+ device_lock(&dev_dax->dev);
+ rc = dev_dax_probe(&dev_dax->dev);
+ device_unlock(&dev_dax->dev);
+
+ devres_close_group(&dev_dax->dev, dev_dax);
+ if (rc)
+ devres_release_group(&dev_dax->dev, dev_dax);
+
+ return rc;
+}
+
+static int dax_pmem_compat_release(struct device *dev, void *data)
+{
+ device_lock(dev);
+ devres_release_group(dev, to_dev_dax(dev));
+ device_unlock(dev);
+
+ return 0;
+}
+
+static int dax_pmem_compat_remove(struct device *dev)
+{
+ device_for_each_child(dev, NULL, dax_pmem_compat_release);
+ return 0;
+}
+
+static struct nd_device_driver dax_pmem_compat_driver = {
+ .probe = dax_pmem_compat_probe,
+ .remove = dax_pmem_compat_remove,
+ .drv = {
+ .name = "dax_pmem_compat",
+ },
+ .type = ND_DRIVER_DAX_PMEM,
+};
+
+static int __init dax_pmem_compat_init(void)
+{
+ return nd_driver_register(&dax_pmem_compat_driver);
+}
+module_init(dax_pmem_compat_init);
+
+static void __exit dax_pmem_compat_exit(void)
+{
+ driver_unregister(&dax_pmem_compat_driver.drv);
+}
+module_exit(dax_pmem_compat_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Intel Corporation");
+MODULE_ALIAS_ND_DEVICE(ND_DEVICE_DAX_PMEM);
diff --git a/drivers/dax/pmem/core.c b/drivers/dax/pmem/core.c
new file mode 100644
index 000000000000..bdcff1b14e95
--- /dev/null
+++ b/drivers/dax/pmem/core.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016 - 2018 Intel Corporation. All rights reserved. */
+#include <linux/memremap.h>
+#include <linux/module.h>
+#include <linux/pfn_t.h>
+#include "../../nvdimm/pfn.h"
+#include "../../nvdimm/nd.h"
+#include "../bus.h"
+
+struct dev_dax *__dax_pmem_probe(struct device *dev, enum dev_dax_subsys subsys)
+{
+ struct resource res;
+ int rc, id, region_id;
+ resource_size_t offset;
+ struct nd_pfn_sb *pfn_sb;
+ struct dev_dax *dev_dax;
+ struct nd_namespace_io *nsio;
+ struct dax_region *dax_region;
+ struct dev_pagemap pgmap = { 0 };
+ struct nd_namespace_common *ndns;
+ struct nd_dax *nd_dax = to_nd_dax(dev);
+ struct nd_pfn *nd_pfn = &nd_dax->nd_pfn;
+
+ ndns = nvdimm_namespace_common_probe(dev);
+ if (IS_ERR(ndns))
+ return ERR_CAST(ndns);
+ nsio = to_nd_namespace_io(&ndns->dev);
+
+ /* parse the 'pfn' info block via ->rw_bytes */
+ rc = devm_nsio_enable(dev, nsio);
+ if (rc)
+ return ERR_PTR(rc);
+ rc = nvdimm_setup_pfn(nd_pfn, &pgmap);
+ if (rc)
+ return ERR_PTR(rc);
+ devm_nsio_disable(dev, nsio);
+
+ /* reserve the metadata area, device-dax will reserve the data */
+ pfn_sb = nd_pfn->pfn_sb;
+ offset = le64_to_cpu(pfn_sb->dataoff);
+ if (!devm_request_mem_region(dev, nsio->res.start, offset,
+ dev_name(&ndns->dev))) {
+ dev_warn(dev, "could not reserve metadata\n");
+ return ERR_PTR(-EBUSY);
+ }
+
+ rc = sscanf(dev_name(&ndns->dev), "namespace%d.%d", &region_id, &id);
+ if (rc != 2)
+ return ERR_PTR(-EINVAL);
+
+ /* adjust the dax_region resource to the start of data */
+ memcpy(&res, &pgmap.res, sizeof(res));
+ res.start += offset;
+ dax_region = alloc_dax_region(dev, region_id, &res,
+ le32_to_cpu(pfn_sb->align), PFN_DEV|PFN_MAP);
+ if (!dax_region)
+ return ERR_PTR(-ENOMEM);
+
+ dev_dax = __devm_create_dev_dax(dax_region, id, &pgmap, subsys);
+
+ /* child dev_dax instances now own the lifetime of the dax_region */
+ dax_region_put(dax_region);
+
+ return dev_dax;
+}
+EXPORT_SYMBOL_GPL(__dax_pmem_probe);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Intel Corporation");
diff --git a/drivers/dax/pmem/pmem.c b/drivers/dax/pmem/pmem.c
new file mode 100644
index 000000000000..0ae4238a0ef8
--- /dev/null
+++ b/drivers/dax/pmem/pmem.c
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016 - 2018 Intel Corporation. All rights reserved. */
+#include <linux/percpu-refcount.h>
+#include <linux/memremap.h>
+#include <linux/module.h>
+#include <linux/pfn_t.h>
+#include <linux/nd.h>
+#include "../bus.h"
+
+static int dax_pmem_probe(struct device *dev)
+{
+ return PTR_ERR_OR_ZERO(__dax_pmem_probe(dev, DEV_DAX_BUS));
+}
+
+static struct nd_device_driver dax_pmem_driver = {
+ .probe = dax_pmem_probe,
+ .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");
+#if !IS_ENABLED(CONFIG_DEV_DAX_PMEM_COMPAT)
+/* For compat builds, don't load this module by default */
+MODULE_ALIAS_ND_DEVICE(ND_DEVICE_DAX_PMEM);
+#endif
diff --git a/tools/testing/nvdimm/Kbuild b/tools/testing/nvdimm/Kbuild
index bfc4d8e98452..1e37719bc37e 100644
--- a/tools/testing/nvdimm/Kbuild
+++ b/tools/testing/nvdimm/Kbuild
@@ -34,6 +34,8 @@ obj-$(CONFIG_DAX) += dax.o
endif
obj-$(CONFIG_DEV_DAX) += device_dax.o
obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem.o
+obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem_core.o
+obj-$(CONFIG_DEV_DAX_PMEM_COMPAT) += dax_pmem_compat.o

nfit-y := $(ACPI_SRC)/core.o
nfit-$(CONFIG_X86_MCE) += $(ACPI_SRC)/mce.o
@@ -63,7 +65,9 @@ device_dax-y += dax-dev.o
device_dax-y += device_dax_test.o
device_dax-y += config_check.o

-dax_pmem-y := $(DAX_SRC)/pmem.o
+dax_pmem-y := $(DAX_SRC)/pmem/pmem.o
+dax_pmem_core-y := $(DAX_SRC)/pmem/core.o
+dax_pmem_compat-y := $(DAX_SRC)/pmem/compat.o
dax_pmem-y += config_check.o

libnvdimm-y := $(NVDIMM_SRC)/core.o