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vfio: Remove extra put/gets around vfio_device->group
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>
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1 changed files with 2 additions and 19 deletions
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@ -546,14 +546,12 @@ struct vfio_device *vfio_group_create_device(struct vfio_group *group,
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kref_init(&device->kref);
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device->dev = dev;
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/* Our reference on group is moved to the device */
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device->group = group;
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device->ops = ops;
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device->device_data = device_data;
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dev_set_drvdata(dev, device);
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/* No need to get group_lock, caller has group reference */
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vfio_group_get(group);
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mutex_lock(&group->device_lock);
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list_add(&device->group_next, &group->device_list);
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group->dev_counter++;
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@ -585,13 +583,11 @@ void vfio_device_put(struct vfio_device *device)
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{
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struct vfio_group *group = device->group;
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kref_put_mutex(&device->kref, vfio_device_release, &group->device_lock);
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vfio_group_put(group);
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}
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EXPORT_SYMBOL_GPL(vfio_device_put);
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static void vfio_device_get(struct vfio_device *device)
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{
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vfio_group_get(device->group);
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kref_get(&device->kref);
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}
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@ -841,14 +837,6 @@ int vfio_add_group_dev(struct device *dev,
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vfio_group_put(group);
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return PTR_ERR(device);
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}
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/*
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* Drop all but the vfio_device reference. The vfio_device holds
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* a reference to the vfio_group, which holds a reference to the
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* iommu_group.
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*/
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vfio_group_put(group);
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return 0;
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}
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EXPORT_SYMBOL_GPL(vfio_add_group_dev);
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@ -928,12 +916,6 @@ void *vfio_del_group_dev(struct device *dev)
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unsigned int i = 0;
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bool interrupted = false;
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/*
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* The group exists so long as we have a device reference. Get
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* a group reference and use it to scan for the device going away.
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*/
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vfio_group_get(group);
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/*
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* When the device is removed from the group, the group suddenly
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* becomes non-viable; the device has a driver (until the unbind
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@ -1008,6 +990,7 @@ void *vfio_del_group_dev(struct device *dev)
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if (list_empty(&group->device_list))
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wait_event(group->container_q, !group->container);
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/* Matches the get in vfio_group_create_device() */
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vfio_group_put(group);
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return device_data;
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