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>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index 0083cbf99edf..df4b03e035bc 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -969,7 +969,7 @@ static int vmw_driver_open(struct drm_device *dev, struct drm_file *file_priv)
                 goto out_no_shman;
 
         file_priv->driver_priv = vmw_fp;
-        dev_priv->bdev.dev_mapping = dev->dev_mapping;
+        dev_priv->bdev.dev_mapping = dev->anon_inode->i_mapping;
 
         return 0;