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Subject[PATCH 7/8] device-dax: Add support for a dax override driver
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Introduce the 'new_id' concept for enabling a custom device-driver attach
policy for dax-bus drivers. The intended use is to have a mechanism for
hot-plugging device-dax ranges into the page allocator on-demand. With
this in place the default policy of using device-dax for performance
differentiated memory can be overridden by user-space policy that can
arrange for the memory range to be managed as 'System RAM' with
user-defined NUMA and other performance attributes.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/dax/bus.c | 145 ++++++++++++++++++++++++++++++++++++++++++++++++--
drivers/dax/bus.h | 10 +++
drivers/dax/device.c | 11 ++--
3 files changed, 156 insertions(+), 10 deletions(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 69aae2cbd45f..178d76504f79 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -2,11 +2,21 @@
/* 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 "dax-private.h"
#include "bus.h"

+static DEFINE_MUTEX(dax_bus_lock);
+
+#define DAX_NAME_LEN 30
+struct dax_id {
+ struct list_head list;
+ char dev_name[DAX_NAME_LEN];
+};
+
static int dax_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
{
/*
@@ -16,22 +26,115 @@ static int dax_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
return add_uevent_var(env, "MODALIAS=" DAX_DEVICE_MODALIAS_FMT, 0);
}

+static struct dax_device_driver *to_dax_drv(struct device_driver *drv)
+{
+ return container_of(drv, struct dax_device_driver, drv);
+}
+
+static struct dax_id *__dax_match_id(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 (strcmp(dax_id->dev_name, dev_name) == 0)
+ return dax_id;
+ return NULL;
+}
+
+static int dax_match_id(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 ssize_t do_id_store(struct device_driver *drv, const char *buf,
+ size_t count, bool add)
+{
+ struct dax_device_driver *dax_drv = to_dax_drv(drv);
+ unsigned int region_id, id;
+ 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;
+
+ if (strlen(buf) + 1 > DAX_NAME_LEN)
+ return -EINVAL;
+
+ mutex_lock(&dax_bus_lock);
+ dax_id = __dax_match_id(dax_drv, buf);
+ if (!dax_id) {
+ if (add) {
+ dax_id = kzalloc(sizeof(*dax_id), GFP_KERNEL);
+ if (dax_id) {
+ strncpy(dax_id->dev_name, buf, DAX_NAME_LEN);
+ list_add(&dax_id->list, &dax_drv->ids);
+ } else
+ rc = -ENOMEM;
+ } else
+ /* nothing to remove */;
+ } else if (!add) {
+ list_del(&dax_id->list);
+ kfree(dax_id);
+ } else
+ /* dax_id already added */;
+ mutex_unlock(&dax_bus_lock);
+ return rc;
+}
+
+static ssize_t new_id_store(struct device_driver *drv, const char *buf,
+ size_t count)
+{
+ return do_id_store(drv, buf, count, true);
+}
+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, false);
+}
+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, struct device_driver *drv);

static struct bus_type dax_bus_type = {
.name = "dax",
.uevent = dax_bus_uevent,
.match = dax_bus_match,
+ .drv_groups = dax_drv_groups,
};

static int dax_bus_match(struct device *dev, struct device_driver *drv)
{
+ struct dax_device_driver *dax_drv = to_dax_drv(drv);
+
/*
- * The drivers that can register on the 'dax' bus are private to
- * drivers/dax/ so any device and driver on the bus always
- * match.
+ * All but the 'device-dax' driver, which has 'match_always'
+ * set, requires an exact id match.
*/
- return 1;
+ if (dax_drv->match_always)
+ return 1;
+
+ return dax_match_id(dax_drv, dev);
}

/*
@@ -273,17 +376,49 @@ struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region, int id,
}
EXPORT_SYMBOL_GPL(devm_create_dev_dax);

-int __dax_driver_register(struct device_driver *drv,
+static int match_always_count;
+
+int __dax_driver_register(struct dax_device_driver *dax_drv,
struct module *module, const char *mod_name)
{
+ struct device_driver *drv = &dax_drv->drv;
+ int rc = 0;
+
+ INIT_LIST_HEAD(&dax_drv->ids);
drv->owner = module;
drv->name = mod_name;
drv->mod_name = mod_name;
drv->bus = &dax_bus_type;
+
+ /* there can only be one default driver */
+ mutex_lock(&dax_bus_lock);
+ match_always_count += dax_drv->match_always;
+ if (match_always_count > 1) {
+ match_always_count--;
+ WARN_ON(1);
+ rc = -EINVAL;
+ }
+ mutex_unlock(&dax_bus_lock);
+ if (rc)
+ return rc;
return driver_register(drv);
}
EXPORT_SYMBOL_GPL(__dax_driver_register);

+void dax_driver_unregister(struct dax_device_driver *dax_drv)
+{
+ struct dax_id *dax_id, *_id;
+
+ mutex_lock(&dax_bus_lock);
+ match_always_count -= dax_drv->match_always;
+ 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);
+}
+EXPORT_SYMBOL_GPL(dax_driver_unregister);
+
int __init dax_bus_init(void)
{
return bus_register(&dax_bus_type);
diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
index e08e0c394983..395ab812367c 100644
--- a/drivers/dax/bus.h
+++ b/drivers/dax/bus.h
@@ -12,10 +12,18 @@ 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);
-int __dax_driver_register(struct device_driver *drv,
+
+struct dax_device_driver {
+ struct device_driver drv;
+ struct list_head ids;
+ int match_always;
+};
+
+int __dax_driver_register(struct dax_device_driver *dax_drv,
struct module *module, const char *mod_name);
#define dax_driver_register(driver) \
__dax_driver_register(driver, THIS_MODULE, KBUILD_MODNAME)
+void dax_driver_unregister(struct dax_device_driver *dax_drv);
void kill_dev_dax(struct dev_dax *dev_dax);

/*
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 967bab097013..052aed3ab600 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -508,9 +508,12 @@ static int dev_dax_remove(struct device *dev)
return 0;
}

-static struct device_driver device_dax_driver = {
- .probe = dev_dax_probe,
- .remove = dev_dax_remove,
+static struct dax_device_driver device_dax_driver = {
+ .drv = {
+ .probe = dev_dax_probe,
+ .remove = dev_dax_remove,
+ },
+ .match_always = 1,
};

static int __init dax_init(void)
@@ -520,7 +523,7 @@ static int __init dax_init(void)

static void __exit dax_exit(void)
{
- driver_unregister(&device_dax_driver);
+ dax_driver_unregister(&device_dax_driver);
}

MODULE_AUTHOR("Intel Corporation");
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