From: Jason Gunthorpe jgg@nvidia.com
[ Upstream commit e572bfb2b6a83b05acd30c03010e661b1967960f ]
The vfio_device->group value has a get obtained during vfio_add_group_dev() which gets moved from the stack to vfio_device->group in vfio_group_create_device().
The reference remains until we reach the end of vfio_del_group_dev() when it is put back.
Thus anything that already has a kref on the vfio_device is guaranteed a valid group pointer. Remove all the extra reference traffic.
It is tricky to see, but the get at the start of vfio_del_group_dev() is actually pairing with the put hidden inside vfio_device_put() a few lines below.
A later patch merges vfio_group_create_device() into vfio_add_group_dev() which makes the ownership and error flow on the create side easier to follow.
Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Kevin Tian kevin.tian@intel.com Reviewed-by: Max Gurtovoy mgurtovoy@nvidia.com Reviewed-by: Cornelia Huck cohuck@redhat.com Reviewed-by: Eric Auger eric.auger@redhat.com Signed-off-by: Jason Gunthorpe jgg@nvidia.com Message-Id: 1-v3-225de1400dfc+4e074-vfio1_jgg@nvidia.com Signed-off-by: Alex Williamson alex.williamson@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/vfio/vfio.c | 21 ++------------------- 1 file changed, 2 insertions(+), 19 deletions(-)
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index 2151bc7f87ab..e1b6e1b51d41 100644 --- a/drivers/vfio/vfio.c +++ b/drivers/vfio/vfio.c @@ -546,14 +546,12 @@ struct vfio_device *vfio_group_create_device(struct vfio_group *group,
kref_init(&device->kref); device->dev = dev; + /* Our reference on group is moved to the device */ device->group = group; device->ops = ops; device->device_data = device_data; dev_set_drvdata(dev, device);
- /* No need to get group_lock, caller has group reference */ - vfio_group_get(group); - mutex_lock(&group->device_lock); list_add(&device->group_next, &group->device_list); group->dev_counter++; @@ -585,13 +583,11 @@ void vfio_device_put(struct vfio_device *device) { struct vfio_group *group = device->group; kref_put_mutex(&device->kref, vfio_device_release, &group->device_lock); - vfio_group_put(group); } EXPORT_SYMBOL_GPL(vfio_device_put);
static void vfio_device_get(struct vfio_device *device) { - vfio_group_get(device->group); kref_get(&device->kref); }
@@ -841,14 +837,6 @@ int vfio_add_group_dev(struct device *dev, vfio_group_put(group); return PTR_ERR(device); } - - /* - * Drop all but the vfio_device reference. The vfio_device holds - * a reference to the vfio_group, which holds a reference to the - * iommu_group. - */ - vfio_group_put(group); - return 0; } EXPORT_SYMBOL_GPL(vfio_add_group_dev); @@ -928,12 +916,6 @@ void *vfio_del_group_dev(struct device *dev) unsigned int i = 0; bool interrupted = false;
- /* - * The group exists so long as we have a device reference. Get - * a group reference and use it to scan for the device going away. - */ - vfio_group_get(group); - /* * When the device is removed from the group, the group suddenly * becomes non-viable; the device has a driver (until the unbind @@ -1008,6 +990,7 @@ void *vfio_del_group_dev(struct device *dev) if (list_empty(&group->device_list)) wait_event(group->container_q, !group->container);
+ /* Matches the get in vfio_group_create_device() */ vfio_group_put(group);
return device_data;