[09/12] vfio/mdev: Remove mdev_parent_ops dev_attr_groups

Commit Message

Jason Gunthorpe April 23, 2021, 11:03 p.m. UTC

This is only used by one sample to print a fixed string that is pointless.

In general, having a device driver attach sysfs attributes to the parent
is horrific. This should never happen, and always leads to some kind of
liftime bug as it become very difficult for the sysfs attribute to go back
to any data owned by the device driver.

Remove the general mechanism to create this abuse.

Signed-off-by: Jason Gunthorpe <[e-mail]>
---
 drivers/vfio/mdev/mdev_sysfs.c | 12 ++----------
 include/linux/mdev.h           |  2 --
 samples/vfio-mdev/mtty.c       | 30 +-----------------------------
 3 files changed, 3 insertions(+), 41 deletions(-)

Comments

Christoph Hellwig April 26, 2021, 2:14 p.m. UTC | #1

On Fri, Apr 23, 2021 at 08:03:06PM -0300, Jason Gunthorpe wrote:
> This is only used by one sample to print a fixed string that is pointless.
> 
> In general, having a device driver attach sysfs attributes to the parent
> is horrific. This should never happen, and always leads to some kind of
> liftime bug as it become very difficult for the sysfs attribute to go back
> to any data owned by the device driver.
> 
> Remove the general mechanism to create this abuse.

Looks good,

Reviewed-by: Christoph Hellwig <[e-mail]>

Patch

diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c
index f5cf1931c54e48..66eef08833a4ef 100644
--- a/drivers/vfio/mdev/mdev_sysfs.c
+++ b/drivers/vfio/mdev/mdev_sysfs.c
@@ -197,7 +197,6 @@  void parent_remove_sysfs_files(struct mdev_parent *parent)
 		remove_mdev_supported_type(type);
 	}
 
-	sysfs_remove_groups(&parent->dev->kobj, parent->ops->dev_attr_groups);
 	kset_unregister(parent->mdev_types_kset);
 }
 
@@ -213,17 +212,10 @@  int parent_create_sysfs_files(struct mdev_parent *parent)
 
 	INIT_LIST_HEAD(&parent->type_list);
 
-	ret = sysfs_create_groups(&parent->dev->kobj,
-				  parent->ops->dev_attr_groups);
-	if (ret)
-		goto create_err;
-
 	ret = add_mdev_supported_type_groups(parent);
 	if (ret)
-		sysfs_remove_groups(&parent->dev->kobj,
-				    parent->ops->dev_attr_groups);
-	else
-		return ret;
+		goto create_err;
+	return 0;
 
 create_err:
 	kset_unregister(parent->mdev_types_kset);
diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index ea48c401e4fa63..fd9fe1dcf0e230 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -57,7 +57,6 @@  struct device *mtype_get_parent_dev(struct mdev_type *mtype);
  *
  * @owner:		The module owner.
  * @device_driver:	Which device driver to probe() on newly created devices
- * @dev_attr_groups:	Attributes of the parent device.
  * @mdev_attr_groups:	Attributes of the mediated device.
  * @supported_type_groups: Attributes to define supported types. It is mandatory
  *			to provide supported types.
@@ -67,7 +66,6 @@  struct device *mtype_get_parent_dev(struct mdev_type *mtype);
 struct mdev_parent_ops {
 	struct module   *owner;
 	struct mdev_driver *device_driver;
-	const struct attribute_group **dev_attr_groups;
 	const struct attribute_group **mdev_attr_groups;
 	struct attribute_group **supported_type_groups;
 };
diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index d2a168420b775d..31eec76bc553ce 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -1207,38 +1207,11 @@  static void mtty_close(struct vfio_device *mdev)
 	pr_info("%s\n", __func__);
 }
 
-static ssize_t
-sample_mtty_dev_show(struct device *dev, struct device_attribute *attr,
-		     char *buf)
-{
-	return sprintf(buf, "This is phy device\n");
-}
-
-static DEVICE_ATTR_RO(sample_mtty_dev);
-
-static struct attribute *mtty_dev_attrs[] = {
-	&dev_attr_sample_mtty_dev.attr,
-	NULL,
-};
-
-static const struct attribute_group mtty_dev_group = {
-	.name  = "mtty_dev",
-	.attrs = mtty_dev_attrs,
-};
-
-static const struct attribute_group *mtty_dev_groups[] = {
-	&mtty_dev_group,
-	NULL,
-};
-
 static ssize_t
 sample_mdev_dev_show(struct device *dev, struct device_attribute *attr,
 		     char *buf)
 {
-	if (mdev_from_dev(dev))
-		return sprintf(buf, "This is MDEV %s\n", dev_name(dev));
-
-	return sprintf(buf, "\n");
+	return sprintf(buf, "This is MDEV %s\n", dev_name(dev));
 }
 
 static DEVICE_ATTR_RO(sample_mdev_dev);
@@ -1340,7 +1313,6 @@  static struct mdev_driver mtty_driver = {
 static const struct mdev_parent_ops mdev_fops = {
 	.owner                  = THIS_MODULE,
 	.device_driver		= &mtty_driver,
-	.dev_attr_groups        = mtty_dev_groups,
 	.supported_type_groups  = mdev_type_groups,
 };