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Subject[PATCH 5/8] device-dax: Introduce bus + driver model
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In support of multiple device-dax instances per device-dax-region and
allowing the 'kmem' driver to attach to dax-instances instead of the
current device-node access, convert the dax sub-system from a class to a
bus. Recall that the kmem driver takes reserved / special purpose
memories and assigns them to be managed by the core-mm.

Aside from the fact the device-dax instances are registered and probed
on a bus, two other lifetime-management changes are made:

1/ Delay attaching a cdev until driver probe time

2/ A new run_dax() helper is introduced to allow restoring dax-operation
after a kill_dax() event. So, at driver ->probe() time we run_dax()
and at ->remove() time we kill_dax() and invalidate all mappings.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/dax/bus.c | 133 ++++++++++++++++++++++++++++++++++++++++++---
drivers/dax/bus.h | 16 +++++
drivers/dax/dax-private.h | 6 +-
drivers/dax/device.c | 95 +++++++++++---------------------
drivers/dax/super.c | 40 +++++++++-----
5 files changed, 203 insertions(+), 87 deletions(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 8a398e8e1956..0cff32102c4c 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -6,6 +6,33 @@
#include "dax-private.h"
#include "bus.h"

+static int dax_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+ /*
+ * We only ever expect to handle device-dax instances, i.e. the
+ * @type argument to MODULE_ALIAS_DAX_DEVICE() is always zero
+ */
+ return add_uevent_var(env, "MODALIAS=" DAX_DEVICE_MODALIAS_FMT, 0);
+}
+
+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,
+};
+
+static int dax_bus_match(struct device *dev, struct device_driver *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.
+ */
+ return 1;
+}
+
/*
* Rely on the fact that drvdata is set before the attributes are
* registered, and that the attributes are unregistered before drvdata
@@ -142,11 +169,10 @@ static const struct attribute_group dev_dax_attribute_group = {
.attrs = dev_dax_attributes,
};

-const struct attribute_group *dax_attribute_groups[] = {
+static const struct attribute_group *dax_attribute_groups[] = {
&dev_dax_attribute_group,
NULL,
};
-EXPORT_SYMBOL_GPL(dax_attribute_groups);

void kill_dev_dax(struct dev_dax *dev_dax)
{
@@ -158,17 +184,108 @@ void kill_dev_dax(struct dev_dax *dev_dax)
}
EXPORT_SYMBOL_GPL(kill_dev_dax);

-void unregister_dev_dax(void *dev)
+static void dev_dax_release(struct device *dev)
{
struct dev_dax *dev_dax = to_dev_dax(dev);
+ struct dax_region *dax_region = dev_dax->region;
struct dax_device *dax_dev = dev_dax->dax_dev;
- struct inode *inode = dax_inode(dax_dev);
- struct cdev *cdev = inode->i_cdev;

- dev_dbg(dev, "trace\n");
+ dax_region_put(dax_region);
+ put_dax(dax_dev);
+ kfree(dev_dax);
+}
+
+static void unregister_dev_dax(void *dev)
+{
+ struct dev_dax *dev_dax = to_dev_dax(dev);
+
+ dev_dbg(dev, "%s\n", __func__);

kill_dev_dax(dev_dax);
- cdev_device_del(cdev, dev);
+ device_del(dev);
put_device(dev);
}
-EXPORT_SYMBOL_GPL(unregister_dev_dax);
+
+struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region, int id)
+{
+ struct device *parent = dax_region->dev;
+ struct dax_device *dax_dev;
+ struct dev_dax *dev_dax;
+ struct inode *inode;
+ struct device *dev;
+ int rc = -ENOMEM;
+
+ if (id < 0)
+ return ERR_PTR(-EINVAL);
+
+ dev_dax = kzalloc(sizeof(*dev_dax), GFP_KERNEL);
+ if (!dev_dax)
+ return ERR_PTR(-ENOMEM);
+
+ /*
+ * No 'host' or dax_operations since there is no access to this
+ * device outside of mmap of the resulting character device.
+ */
+ dax_dev = alloc_dax(dev_dax, NULL, NULL);
+ if (!dax_dev)
+ goto err;
+
+ /* a device_dax instance is dead while the driver is not attached */
+ kill_dax(dax_dev);
+
+ /* from here on we're committed to teardown via dax_dev_release() */
+ dev = &dev_dax->dev;
+ device_initialize(dev);
+
+ dev_dax->dax_dev = dax_dev;
+ dev_dax->region = dax_region;
+ kref_get(&dax_region->kref);
+
+ inode = dax_inode(dax_dev);
+ dev->devt = inode->i_rdev;
+ dev->bus = &dax_bus_type;
+ dev->parent = parent;
+ dev->groups = dax_attribute_groups;
+ dev->release = dev_dax_release;
+ dev_set_name(dev, "dax%d.%d", dax_region->id, id);
+
+ rc = device_add(dev);
+ if (rc) {
+ kill_dev_dax(dev_dax);
+ put_device(dev);
+ return ERR_PTR(rc);
+ }
+
+ rc = devm_add_action_or_reset(dax_region->dev, unregister_dev_dax, dev);
+ if (rc)
+ return ERR_PTR(rc);
+
+ return dev_dax;
+
+ err:
+ kfree(dev_dax);
+
+ return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_GPL(devm_create_dev_dax);
+
+int __dax_driver_register(struct device_driver *drv,
+ struct module *module, const char *mod_name)
+{
+ drv->owner = module;
+ drv->name = mod_name;
+ drv->mod_name = mod_name;
+ drv->bus = &dax_bus_type;
+ return driver_register(drv);
+}
+EXPORT_SYMBOL_GPL(__dax_driver_register);
+
+int __init dax_bus_init(void)
+{
+ return bus_register(&dax_bus_type);
+}
+
+void __exit dax_bus_exit(void)
+{
+ bus_unregister(&dax_bus_type);
+}
diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
index 840865aa69e8..ea509504df3a 100644
--- a/drivers/dax/bus.h
+++ b/drivers/dax/bus.h
@@ -11,5 +11,21 @@ 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);
+int __dax_driver_register(struct device_driver *drv,
+ struct module *module, const char *mod_name);
+#define dax_driver_register(driver) \
+ __dax_driver_register(driver, THIS_MODULE, KBUILD_MODNAME)
void kill_dev_dax(struct dev_dax *dev_dax);
+
+/*
+ * 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
+ * outside of drivers/dax/
+ */
+void run_dax(struct dax_device *dax_dev);
+
+#define MODULE_ALIAS_DAX_DEVICE(type) \
+ MODULE_ALIAS("dax:t" __stringify(type) "*")
+#define DAX_DEVICE_MODALIAS_FMT "dax:t%d"
+
#endif /* __DAX_BUS_H__ */
diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
index 620c3f4eefe7..c3a121700837 100644
--- a/drivers/dax/dax-private.h
+++ b/drivers/dax/dax-private.h
@@ -20,10 +20,8 @@
struct dax_device;
struct dax_device *inode_dax(struct inode *inode);
struct inode *dax_inode(struct dax_device *dax_dev);
-
-/* temporary until devm_create_dax_dev moves to bus.c */
-extern const struct attribute_group *dax_attribute_groups[];
-void unregister_dev_dax(void *dev);
+int dax_bus_init(void);
+void dax_bus_exit(void);

/**
* struct dax_region - mapping infrastructure for dax devices
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 1fc375783e0b..f55829404a24 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -13,8 +13,6 @@
#include "dax-private.h"
#include "bus.h"

-static struct class *dax_class;
-
static int check_vma(struct dev_dax *dev_dax, struct vm_area_struct *vma,
const char *func)
{
@@ -404,93 +402,64 @@ static const struct file_operations dax_fops = {
.mmap_supported_flags = MAP_SYNC,
};

-static void dev_dax_release(struct device *dev)
+static void dev_dax_cdev_del(void *cdev)
{
- struct dev_dax *dev_dax = to_dev_dax(dev);
- struct dax_region *dax_region = dev_dax->region;
- struct dax_device *dax_dev = dev_dax->dax_dev;
+ cdev_del(cdev);
+}

- dax_region_put(dax_region);
- put_dax(dax_dev);
- kfree(dev_dax);
+static void dev_dax_kill(void *dev_dax)
+{
+ kill_dev_dax(dev_dax);
}

-struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region, int id)
+static int dev_dax_probe(struct device *dev)
{
- struct device *parent = dax_region->dev;
- struct dax_device *dax_dev;
- struct dev_dax *dev_dax;
+ struct dev_dax *dev_dax = to_dev_dax(dev);
+ struct dax_device *dax_dev = dev_dax->dax_dev;
struct inode *inode;
- struct device *dev;
struct cdev *cdev;
int rc;

- dev_dax = kzalloc(sizeof(*dev_dax), GFP_KERNEL);
- if (!dev_dax)
- return ERR_PTR(-ENOMEM);
-
- /*
- * No 'host' or dax_operations since there is no access to this
- * device outside of mmap of the resulting character device.
- */
- dax_dev = alloc_dax(dev_dax, NULL, NULL);
- if (!dax_dev) {
- rc = -ENOMEM;
- goto err;
- }
-
- /* from here on we're committed to teardown via dax_dev_release() */
- dev = &dev_dax->dev;
- device_initialize(dev);
-
inode = dax_inode(dax_dev);
cdev = inode->i_cdev;
cdev_init(cdev, &dax_fops);
- cdev->owner = parent->driver->owner;
-
- dev_dax->dax_dev = dax_dev;
- dev_dax->region = dax_region;
- kref_get(&dax_region->kref);
-
- dev->devt = inode->i_rdev;
- dev->class = dax_class;
- dev->parent = parent;
- dev->groups = dax_attribute_groups;
- dev->release = dev_dax_release;
- dev_set_name(dev, "dax%d.%d", dax_region->id, id);
-
- rc = cdev_device_add(cdev, dev);
- if (rc) {
- kill_dev_dax(dev_dax);
- put_device(dev);
- return ERR_PTR(rc);
- }
-
- rc = devm_add_action_or_reset(dax_region->dev, unregister_dev_dax, dev);
+ cdev->owner = dev->driver->owner;
+ cdev_set_parent(cdev, &dev->kobj);
+ rc = cdev_add(cdev, dev->devt, 1);
if (rc)
- return ERR_PTR(rc);
+ return rc;

- return dev_dax;
+ rc = devm_add_action_or_reset(dev, dev_dax_cdev_del, cdev);
+ if (rc)
+ return rc;

- err:
- kfree(dev_dax);
+ run_dax(dax_dev);
+ return devm_add_action_or_reset(dev, dev_dax_kill, dev_dax);
+}

- return ERR_PTR(rc);
+static int dev_dax_remove(struct device *dev)
+{
+ /* all probe actions are unwound by devm */
+ return 0;
}
-EXPORT_SYMBOL_GPL(devm_create_dev_dax);
+
+static struct device_driver device_dax_driver = {
+ .probe = dev_dax_probe,
+ .remove = dev_dax_remove,
+};

static int __init dax_init(void)
{
- dax_class = class_create(THIS_MODULE, "dax");
- return PTR_ERR_OR_ZERO(dax_class);
+ return dax_driver_register(&device_dax_driver);
}

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

MODULE_AUTHOR("Intel Corporation");
MODULE_LICENSE("GPL v2");
-subsys_initcall(dax_init);
+module_init(dax_init);
module_exit(dax_exit);
+MODULE_ALIAS_DAX_DEVICE(0);
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 0ecc1a2cf1cc..ccb22d8db3a2 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -366,11 +366,15 @@ void kill_dax(struct dax_device *dax_dev)
spin_lock(&dax_host_lock);
hlist_del_init(&dax_dev->list);
spin_unlock(&dax_host_lock);
-
- dax_dev->private = NULL;
}
EXPORT_SYMBOL_GPL(kill_dax);

+void run_dax(struct dax_device *dax_dev)
+{
+ set_bit(DAXDEV_ALIVE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(run_dax);
+
static struct inode *dax_alloc_inode(struct super_block *sb)
{
struct dax_device *dax_dev;
@@ -585,6 +589,8 @@ EXPORT_SYMBOL_GPL(dax_inode);

void *dax_get_private(struct dax_device *dax_dev)
{
+ if (!test_bit(DAXDEV_ALIVE, &dax_dev->flags))
+ return NULL;
return dax_dev->private;
}
EXPORT_SYMBOL_GPL(dax_get_private);
@@ -598,7 +604,7 @@ static void init_once(void *_dax_dev)
inode_init_once(inode);
}

-static int __dax_fs_init(void)
+static int dax_fs_init(void)
{
int rc;

@@ -630,35 +636,45 @@ static int __dax_fs_init(void)
return rc;
}

-static void __dax_fs_exit(void)
+static void dax_fs_exit(void)
{
kern_unmount(dax_mnt);
unregister_filesystem(&dax_fs_type);
kmem_cache_destroy(dax_cache);
}

-static int __init dax_fs_init(void)
+static int __init dax_core_init(void)
{
int rc;

- rc = __dax_fs_init();
+ rc = dax_fs_init();
if (rc)
return rc;

rc = alloc_chrdev_region(&dax_devt, 0, MINORMASK+1, "dax");
if (rc)
- __dax_fs_exit();
- return rc;
+ goto err_chrdev;
+
+ rc = dax_bus_init();
+ if (rc)
+ goto err_bus;
+ return 0;
+
+err_bus:
+ unregister_chrdev_region(dax_devt, MINORMASK+1);
+err_chrdev:
+ dax_fs_exit();
+ return 0;
}

-static void __exit dax_fs_exit(void)
+static void __exit dax_core_exit(void)
{
unregister_chrdev_region(dax_devt, MINORMASK+1);
ida_destroy(&dax_minor_ida);
- __dax_fs_exit();
+ dax_fs_exit();
}

MODULE_AUTHOR("Intel Corporation");
MODULE_LICENSE("GPL v2");
-subsys_initcall(dax_fs_init);
-module_exit(dax_fs_exit);
+subsys_initcall(dax_core_init);
+module_exit(dax_core_exit);
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