Revert "drm: drop redundant drm_file->is_master"

This reverts commit 48ba813701eb14b3008edefef4a0789b328e278c.

Thanks to Chris:
"drm_file->is_master is not synomous with having drm_file->master ==
drm_file->minor->master. This is because drm_file->master is the same
for all drm_files of the same generation and so when there is a master,
every drm_file believes itself to be the master. Confusion ensues and
things go pear shaped when one file is closed and there is no master
anymore."

Conflicts:
	drivers/gpu/drm/drm_drv.c
	drivers/gpu/drm/drm_stub.c

1 files changed, 3 insertions, 16 deletions

diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index a57646382086..a12fbbac373c 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -384,6 +384,8 @@ struct drm_prime_file_private {
 /** File private data */
 struct drm_file {
 	unsigned authenticated :1;
+	/* Whether we're master for a minor. Protected by master_mutex */
+	unsigned is_master :1;
 	/* true when the client has asked us to expose stereo 3D mode flags */
 	unsigned stereo_allowed :1;
 	/*
@@ -1020,7 +1022,7 @@ struct drm_device {
 	/** \name Locks */
 	/*@{ */
 	struct mutex struct_mutex;	/**< For others */
-	struct mutex master_mutex;      /**< For drm_minor::master */
+	struct mutex master_mutex;      /**< For drm_minor::master and drm_file::is_master */
 	/*@} */
 
 	/** \name Usage Counters */
@@ -1158,21 +1160,6 @@ static inline bool drm_is_primary_client(const struct drm_file *file_priv)
 	return file_priv->minor->type == DRM_MINOR_LEGACY;
 }
 
-/**
- * drm_is_master() - Check whether a DRM open-file is DRM-Master
- * @file: DRM open-file context
- *
- * This checks whether a DRM open-file context is owner of the master context
- * attached to it. If a file owns a master context, it's called DRM-Master.
- * Per DRM device, only one such file can be DRM-Master at a time.
- *
- * Returns: True if the file is DRM-Master, otherwise false.
- */
-static inline bool drm_is_master(const struct drm_file *file)
-{
-	return file->master && file->master == file->minor->master;
-}
-
 /******************************************************************/
 /** \name Internal function definitions */
 /*@{*/