device-dax: Add support for a dax override driver

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>

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 69aae2c..17af6fb 100644 (file)
--- 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 (sysfs_streq(dax_id->dev_name, dev_name))
+                       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;
+       char devname[DAX_NAME_LEN];
+       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;
+       sprintf(devname, "dax%d.%d", region_id, id);
+       if (!sysfs_streq(buf, devname))
+               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 e08e0c3..395ab81 100644 (file)
--- 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 6ad964d..ad31203 100644 (file)
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -504,9 +504,12 @@ 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)
@@ -516,7 +519,7 @@ 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");