drm: use anon-inode instead of relying on cdevs
DRM drivers share a common address_space across all character-devices of a
single DRM device. This allows simple buffer eviction and mapping-control.
However, DRM core currently waits for the first ->open() on any char-dev
to mark the underlying inode as backing inode of the device. This delayed
initialization causes ugly conditions all over the place:
if (dev->dev_mapping)
do_sth();
To avoid delayed initialization and to stop reusing the inode of the
char-dev, we allocate an anonymous inode for each DRM device and reset
filp->f_mapping to it on ->open().
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 3618bb0..928e15b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1508,7 +1508,8 @@
if (!obj->fault_mappable)
return;
- drm_vma_node_unmap(&obj->base.vma_node, obj->base.dev->dev_mapping);
+ drm_vma_node_unmap(&obj->base.vma_node,
+ obj->base.dev->anon_inode->i_mapping);
obj->fault_mappable = false;
}