> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Wednesday, March 24, 2021 1:55 AM
>
> mdev_device->type->parent is the same thing.
>
> The struct mdev_device was relying on the kref on the mdev_parent to also
> indirectly hold a kref on the mdev_type pointer. Now that the type holds a
> kref on the parent we can directly kref the mdev_type and remove this
> implicit relationship.
>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> ---
> drivers/vfio/mdev/mdev_core.c | 13 +++++--------
> drivers/vfio/mdev/vfio_mdev.c | 14 +++++++-------
> include/linux/mdev.h | 1 -
> 3 files changed, 12 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/vfio/mdev/mdev_core.c
> b/drivers/vfio/mdev/mdev_core.c
> index 4b5e372ed58f26..493df3da451339 100644
> --- a/drivers/vfio/mdev/mdev_core.c
> +++ b/drivers/vfio/mdev/mdev_core.c
> @@ -29,7 +29,7 @@ static DEFINE_MUTEX(mdev_list_lock);
>
> struct device *mdev_parent_dev(struct mdev_device *mdev)
> {
> - return mdev->parent->dev;
> + return mdev->type->parent->dev;
> }
> EXPORT_SYMBOL(mdev_parent_dev);
>
> @@ -58,12 +58,11 @@ void mdev_release_parent(struct kref *kref)
> /* Caller must hold parent unreg_sem read or write lock */
> static void mdev_device_remove_common(struct mdev_device *mdev)
> {
> - struct mdev_parent *parent;
> + struct mdev_parent *parent = mdev->type->parent;
What about having a wrapper here, like mdev_parent_dev? For
readability it's not necessary to show that the parent is indirectly
retrieved through mdev_type.
> int ret;
>
> mdev_remove_sysfs_files(mdev);
> device_del(&mdev->dev);
> - parent = mdev->parent;
> lockdep_assert_held(&parent->unreg_sem);
> ret = parent->ops->remove(mdev);
> if (ret)
> @@ -212,7 +211,7 @@ static void mdev_device_release(struct device *dev)
> struct mdev_device *mdev = to_mdev_device(dev);
>
> /* Pairs with the get in mdev_device_create() */
> - mdev_put_parent(mdev->parent);
> + kobject_put(&mdev->type->kobj);
Maybe keep mdev_get/put_parent and change them to accept "struct
mdev_device *" parameter like other places.
>
> mutex_lock(&mdev_list_lock);
> list_del(&mdev->next);
> @@ -250,9 +249,8 @@ int mdev_device_create(struct mdev_type *type,
> const guid_t *uuid)
> mdev->dev.release = mdev_device_release;
> mdev->dev.groups = parent->ops->mdev_attr_groups;
> mdev->type = type;
> - mdev->parent = parent;
> /* Pairs with the put in mdev_device_release() */
> - mdev_get_parent(parent);
> + kobject_get(&type->kobj);
>
> guid_copy(&mdev->uuid, uuid);
> list_add(&mdev->next, &mdev_list);
> @@ -300,7 +298,7 @@ int mdev_device_create(struct mdev_type *type,
> const guid_t *uuid)
> int mdev_device_remove(struct mdev_device *mdev)
> {
> struct mdev_device *tmp;
> - struct mdev_parent *parent;
> + struct mdev_parent *parent = mdev->type->parent;
>
> mutex_lock(&mdev_list_lock);
> list_for_each_entry(tmp, &mdev_list, next) {
> @@ -321,7 +319,6 @@ int mdev_device_remove(struct mdev_device *mdev)
> mdev->active = false;
> mutex_unlock(&mdev_list_lock);
>
> - parent = mdev->parent;
> /* Check if parent unregistration has started */
> if (!down_read_trylock(&parent->unreg_sem))
> return -ENODEV;
> diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
> index cc9507ed85a181..922729071c5a8e 100644
> --- a/drivers/vfio/mdev/vfio_mdev.c
> +++ b/drivers/vfio/mdev/vfio_mdev.c
> @@ -24,7 +24,7 @@
> static int vfio_mdev_open(struct vfio_device *core_vdev)
> {
> struct mdev_device *mdev = to_mdev_device(core_vdev->dev);
> - struct mdev_parent *parent = mdev->parent;
> + struct mdev_parent *parent = mdev->type->parent;
>
> int ret;
>
> @@ -44,7 +44,7 @@ static int vfio_mdev_open(struct vfio_device
> *core_vdev)
> static void vfio_mdev_release(struct vfio_device *core_vdev)
> {
> struct mdev_device *mdev = to_mdev_device(core_vdev->dev);
> - struct mdev_parent *parent = mdev->parent;
> + struct mdev_parent *parent = mdev->type->parent;
>
> if (likely(parent->ops->release))
> parent->ops->release(mdev);
> @@ -56,7 +56,7 @@ static long vfio_mdev_unlocked_ioctl(struct vfio_device
> *core_vdev,
> unsigned int cmd, unsigned long arg)
> {
> struct mdev_device *mdev = to_mdev_device(core_vdev->dev);
> - struct mdev_parent *parent = mdev->parent;
> + struct mdev_parent *parent = mdev->type->parent;
>
> if (unlikely(!parent->ops->ioctl))
> return -EINVAL;
> @@ -68,7 +68,7 @@ static ssize_t vfio_mdev_read(struct vfio_device
> *core_vdev, char __user *buf,
> size_t count, loff_t *ppos)
> {
> struct mdev_device *mdev = to_mdev_device(core_vdev->dev);
> - struct mdev_parent *parent = mdev->parent;
> + struct mdev_parent *parent = mdev->type->parent;
>
> if (unlikely(!parent->ops->read))
> return -EINVAL;
> @@ -81,7 +81,7 @@ static ssize_t vfio_mdev_write(struct vfio_device
> *core_vdev,
> loff_t *ppos)
> {
> struct mdev_device *mdev = to_mdev_device(core_vdev->dev);
> - struct mdev_parent *parent = mdev->parent;
> + struct mdev_parent *parent = mdev->type->parent;
>
> if (unlikely(!parent->ops->write))
> return -EINVAL;
> @@ -93,7 +93,7 @@ static int vfio_mdev_mmap(struct vfio_device
> *core_vdev,
> struct vm_area_struct *vma)
> {
> struct mdev_device *mdev = to_mdev_device(core_vdev->dev);
> - struct mdev_parent *parent = mdev->parent;
> + struct mdev_parent *parent = mdev->type->parent;
>
> if (unlikely(!parent->ops->mmap))
> return -EINVAL;
> @@ -104,7 +104,7 @@ static int vfio_mdev_mmap(struct vfio_device
> *core_vdev,
> static void vfio_mdev_request(struct vfio_device *core_vdev, unsigned int
> count)
> {
> struct mdev_device *mdev = to_mdev_device(core_vdev->dev);
> - struct mdev_parent *parent = mdev->parent;
> + struct mdev_parent *parent = mdev->type->parent;
>
> if (parent->ops->request)
> parent->ops->request(mdev, count);
> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> index 349e8ac1fe3382..fb582adda28a9b 100644
> --- a/include/linux/mdev.h
> +++ b/include/linux/mdev.h
> @@ -14,7 +14,6 @@ struct mdev_type;
>
> struct mdev_device {
> struct device dev;
> - struct mdev_parent *parent;
> guid_t uuid;
> void *driver_data;
> struct list_head next;
> --
> 2.31.0
