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

drivers/gpu/drm/drm_crtc.c

@@ -3244,7 +3244,7 @@ int drm_mode_getfb(struct drm_device *dev,
 	r->bpp = fb->bits_per_pixel;
 	r->pitch = fb->pitches[0];
 	if (fb->funcs->create_handle) {
-		if (drm_is_master(file_priv) || capable(CAP_SYS_ADMIN) ||
+		if (file_priv->is_master || capable(CAP_SYS_ADMIN) ||
 		    drm_is_control_client(file_priv)) {
 			ret = fb->funcs->create_handle(fb, file_priv,
 						       &r->handle);

drivers/gpu/drm/drm_drv.c

@@ -179,7 +179,7 @@ int drm_setmaster_ioctl(struct drm_device *dev, void *data,
 	int ret = 0;
 
 	mutex_lock(&dev->master_mutex);
-	if (drm_is_master(file_priv))
+	if (file_priv->is_master)
 		goto out_unlock;
 
 	if (file_priv->minor->master) {
@@ -193,10 +193,13 @@ int drm_setmaster_ioctl(struct drm_device *dev, void *data,
 	}
 
 	file_priv->minor->master = drm_master_get(file_priv->master);
+	file_priv->is_master = 1;
 	if (dev->driver->master_set) {
 		ret = dev->driver->master_set(dev, file_priv, false);
-		if (unlikely(ret != 0))
+		if (unlikely(ret != 0)) {
+			file_priv->is_master = 0;
 			drm_master_put(&file_priv->minor->master);
+		}
 	}
 
 out_unlock:
@@ -210,7 +213,7 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
 	int ret = -EINVAL;
 
 	mutex_lock(&dev->master_mutex);
-	if (!drm_is_master(file_priv))
+	if (!file_priv->is_master)
 		goto out_unlock;
 
 	if (!file_priv->minor->master)
@@ -220,6 +223,7 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
 	if (dev->driver->master_drop)
 		dev->driver->master_drop(dev, file_priv, false);
 	drm_master_put(&file_priv->minor->master);
+	file_priv->is_master = 0;
 
 out_unlock:
 	mutex_unlock(&dev->master_mutex);

drivers/gpu/drm/drm_fops.c

@@ -194,6 +194,7 @@ static int drm_open_helper(struct file *filp, struct drm_minor *minor)
 			goto out_close;
 		}
 
+		priv->is_master = 1;
 		/* take another reference for the copy in the local file priv */
 		priv->master = drm_master_get(priv->minor->master);
 		priv->authenticated = 1;
@@ -425,7 +426,7 @@ int drm_release(struct inode *inode, struct file *filp)
 
 	mutex_lock(&dev->master_mutex);
 
-	if (drm_is_master(file_priv)) {
+	if (file_priv->is_master) {
 		struct drm_master *master = file_priv->master;
 
 		/**
@@ -453,6 +454,7 @@ int drm_release(struct inode *inode, struct file *filp)
 	/* drop the master reference held by the file priv */
 	if (file_priv->master)
 		drm_master_put(&file_priv->master);
+	file_priv->is_master = 0;
 	mutex_unlock(&dev->master_mutex);
 
 	if (dev->driver->postclose)

drivers/gpu/drm/drm_ioctl.c

@@ -607,7 +607,7 @@ static int drm_ioctl_permit(u32 flags, struct drm_file *file_priv)
 		return -EACCES;
 
 	/* MASTER is only for master or control clients */
-	if (unlikely((flags & DRM_MASTER) && !drm_is_master(file_priv) &&
+	if (unlikely((flags & DRM_MASTER) && !file_priv->is_master &&
 		     !drm_is_control_client(file_priv)))
 		return -EACCES;
 

drivers/gpu/drm/drm_lock.c

@@ -112,7 +112,7 @@ int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv)
 	/* don't set the block all signals on the master process for now 
 	 * really probably not the correct answer but lets us debug xkb
  	 * xserver for now */
-	if (!drm_is_master(file_priv)) {
+	if (!file_priv->is_master) {
 		sigemptyset(&dev->sigmask);
 		sigaddset(&dev->sigmask, SIGSTOP);
 		sigaddset(&dev->sigmask, SIGTSTP);

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -1260,7 +1260,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 
 	flags = 0;
 	if (args->flags & I915_EXEC_SECURE) {
-		if (!drm_is_master(file) || !capable(CAP_SYS_ADMIN))
+		if (!file->is_master || !capable(CAP_SYS_ADMIN))
 		    return -EPERM;
 
 		flags |= I915_DISPATCH_SECURE;
@@ -1369,7 +1369,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 		ret = i915_parse_cmds(ring,
 				      batch_obj,
 				      args->batch_start_offset,
-				      drm_is_master(file));
+				      file->is_master);
 		if (ret)
 			goto err;
 

drivers/gpu/drm/vmwgfx/vmwgfx_drv.c

@@ -990,7 +990,7 @@ static struct vmw_master *vmw_master_check(struct drm_device *dev,
 	if (unlikely(ret != 0))
 		return ERR_PTR(-ERESTARTSYS);
 
-	if (drm_is_master(file_priv)) {
+	if (file_priv->is_master) {
 		mutex_unlock(&dev->master_mutex);
 		return NULL;
 	}

drivers/staging/imx-drm/imx-drm-core.c

@@ -182,7 +182,7 @@ static void imx_drm_driver_preclose(struct drm_device *drm,
 {
 	int i;
 
-	if (!drm_is_master(file))
+	if (!file->is_master)
 		return;
 
 	for (i = 0; i < MAX_CRTC; i++)

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 */
 /*@{*/