drm: restore open_count if drm_setup fails

commit 0f1cb1bd upstream.

If drm_setup (called at first open) fails, the whole
open call has failed, so we should not keep the
open_count incremented.
Signed-off-by: Ilija Hadzic <ihadzic@research.bell-labs.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/gpu/drm/drm_fops.c

@@ -136,8 +136,11 @@ int drm_open(struct inode *inode, struct file *filp)
 	retcode = drm_open_helper(inode, filp, dev);
 	if (!retcode) {
 		atomic_inc(&dev->counts[_DRM_STAT_OPENS]);
-		if (!dev->open_count++)
+		if (!dev->open_count++) {
 			retcode = drm_setup(dev);
+			if (retcode)
+				dev->open_count--;
+		}
 	}
 	if (!retcode) {
 		mutex_lock(&dev->struct_mutex);