drm/gem: handlecount isn't really a kref so don't make it one.

There were lots of places being inconsistent since handle count
looked like a kref but it really wasn't.

Fix this my just making handle count an atomic on the object,
and have it increase the normal object kref.

Now i915/radeon/nouveau drivers can drop the normal reference on
userspace object creation, and have the handle hold it.

This patch fixes a memory leak or corruption on unload, because
the driver had no way of knowing if a handle had been actually
added for this object, and the fbcon object needed to know this
to clean itself up properly.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>

11 files changed, 33 insertions, 34 deletions

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 6fe2cd298c12..f7e61be8430a 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -148,7 +148,7 @@ int drm_gem_object_init(struct drm_device *dev,
                 return -ENOMEM;
 
         kref_init(&obj->refcount);
-        kref_init(&obj->handlecount);
+        atomic_set(&obj->handle_count, 0);
         obj->size = size;
 
         atomic_inc(&dev->object_count);
@@ -496,12 +496,8 @@ static void drm_gem_object_ref_bug(struct kref *list_kref)
  * called before drm_gem_object_free or we'll be touching
  * freed memory
  */
-void
-drm_gem_object_handle_free(struct kref *kref)
+void drm_gem_object_handle_free(struct drm_gem_object *obj)
 {
-        struct drm_gem_object *obj = container_of(kref,
-                                                  struct drm_gem_object,
-                                                  handlecount);
         struct drm_device *dev = obj->dev;
 
         /* Remove any name for this object */
diff --git a/drivers/gpu/drm/drm_info.c b/drivers/gpu/drm/drm_info.c
index 2ef2c7827243..974e970ce3f8 100644
--- a/drivers/gpu/drm/drm_info.c
+++ b/drivers/gpu/drm/drm_info.c
@@ -255,7 +255,7 @@ int drm_gem_one_name_info(int id, void *ptr, void *data)
 
         seq_printf(m, "%6d %8zd %7d %8d\n",
                    obj->name, obj->size,
-                   atomic_read(&obj->handlecount.refcount),
+                   atomic_read(&obj->handle_count),
                    atomic_read(&obj->refcount.refcount));
         return 0;
 }
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index cf4ffbee1c00..4cdf74264ee8 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -136,14 +136,12 @@ i915_gem_create_ioctl(struct drm_device *dev, void *data,
                 return -ENOMEM;
 
         ret = drm_gem_handle_create(file_priv, obj, &handle);
+        /* drop reference from allocate - handle holds it now */
+        drm_gem_object_unreference_unlocked(obj);
         if (ret) {
-                drm_gem_object_unreference_unlocked(obj);
                 return ret;
         }
 
-        /* Sink the floating reference from kref_init(handlecount) */
-        drm_gem_object_handle_unreference_unlocked(obj);
-
         args->handle = handle;
         return 0;
 }
diff --git a/drivers/gpu/drm/i915/intel_fb.c b/drivers/gpu/drm/i915/intel_fb.c
index 7bdc96256bf5..56ad9df2ccb5 100644
--- a/drivers/gpu/drm/i915/intel_fb.c
+++ b/drivers/gpu/drm/i915/intel_fb.c
@@ -237,8 +237,10 @@ int intel_fbdev_destroy(struct drm_device *dev,
         drm_fb_helper_fini(&ifbdev->helper);
 
         drm_framebuffer_cleanup(&ifb->base);
-        if (ifb->obj)
+        if (ifb->obj) {
+                drm_gem_object_handle_unreference(ifb->obj);
                 drm_gem_object_unreference(ifb->obj);
+        }
 
         return 0;
 }
diff --git a/drivers/gpu/drm/nouveau/nouveau_fbcon.c b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
index dbd30b2e43fd..d2047713dc59 100644
--- a/drivers/gpu/drm/nouveau/nouveau_fbcon.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
@@ -352,6 +352,7 @@ nouveau_fbcon_destroy(struct drm_device *dev, struct nouveau_fbdev *nfbdev)
 
         if (nouveau_fb->nvbo) {
                 nouveau_bo_unmap(nouveau_fb->nvbo);
+                drm_gem_object_handle_unreference_unlocked(nouveau_fb->nvbo->gem);
                 drm_gem_object_unreference_unlocked(nouveau_fb->nvbo->gem);
                 nouveau_fb->nvbo = NULL;
         }
diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
index ead7b8fc53fc..19620a6709f5 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -167,11 +167,9 @@ nouveau_gem_ioctl_new(struct drm_device *dev, void *data,
                 goto out;
 
         ret = drm_gem_handle_create(file_priv, nvbo->gem, &req->info.handle);
+        /* drop reference from allocate - handle holds it now */
+        drm_gem_object_unreference_unlocked(nvbo->gem);
 out:
-        drm_gem_object_handle_unreference_unlocked(nvbo->gem);
-
-        if (ret)
-                drm_gem_object_unreference_unlocked(nvbo->gem);
         return ret;
 }
 
diff --git a/drivers/gpu/drm/nouveau/nouveau_notifier.c b/drivers/gpu/drm/nouveau/nouveau_notifier.c
index 3ec181ff50ce..3c9964a8fbad 100644
--- a/drivers/gpu/drm/nouveau/nouveau_notifier.c
+++ b/drivers/gpu/drm/nouveau/nouveau_notifier.c
@@ -79,6 +79,7 @@ nouveau_notifier_takedown_channel(struct nouveau_channel *chan)
         mutex_lock(&dev->struct_mutex);
         nouveau_bo_unpin(chan->notifier_bo);
         mutex_unlock(&dev->struct_mutex);
+        drm_gem_object_handle_unreference_unlocked(chan->notifier_bo->gem);
         drm_gem_object_unreference_unlocked(chan->notifier_bo->gem);
         drm_mm_takedown(&chan->notifier_heap);
 }
diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 7422f274615a..b92d2f2fcbed 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -843,8 +843,9 @@ static void radeon_user_framebuffer_destroy(struct drm_framebuffer *fb)
 {
         struct radeon_framebuffer *radeon_fb = to_radeon_framebuffer(fb);
 
-        if (radeon_fb->obj)
+        if (radeon_fb->obj) {
                 drm_gem_object_unreference_unlocked(radeon_fb->obj);
+        }
         drm_framebuffer_cleanup(fb);
         kfree(radeon_fb);
 }
diff --git a/drivers/gpu/drm/radeon/radeon_fb.c b/drivers/gpu/drm/radeon/radeon_fb.c
index c74a8b20d941..9cdf6a35bc2c 100644
--- a/drivers/gpu/drm/radeon/radeon_fb.c
+++ b/drivers/gpu/drm/radeon/radeon_fb.c
@@ -94,8 +94,10 @@ static void radeonfb_destroy_pinned_object(struct drm_gem_object *gobj)
         ret = radeon_bo_reserve(rbo, false);
         if (likely(ret == 0)) {
                 radeon_bo_kunmap(rbo);
+                radeon_bo_unpin(rbo);
                 radeon_bo_unreserve(rbo);
         }
+        drm_gem_object_handle_unreference(gobj);
         drm_gem_object_unreference_unlocked(gobj);
 }
 
@@ -325,8 +327,6 @@ static int radeon_fbdev_destroy(struct drm_device *dev, struct radeon_fbdev *rfb
 {
         struct fb_info *info;
         struct radeon_framebuffer *rfb = &rfbdev->rfb;
-        struct radeon_bo *rbo;
-        int r;
 
         if (rfbdev->helper.fbdev) {
                 info = rfbdev->helper.fbdev;
@@ -338,14 +338,8 @@ static int radeon_fbdev_destroy(struct drm_device *dev, struct radeon_fbdev *rfb
         }
 
         if (rfb->obj) {
-                rbo = rfb->obj->driver_private;
-                r = radeon_bo_reserve(rbo, false);
-                if (likely(r == 0)) {
-                        radeon_bo_kunmap(rbo);
-                        radeon_bo_unpin(rbo);
-                        radeon_bo_unreserve(rbo);
-                }
-                drm_gem_object_unreference_unlocked(rfb->obj);
+                radeonfb_destroy_pinned_object(rfb->obj);
+                rfb->obj = NULL;
         }
         drm_fb_helper_fini(&rfbdev->helper);
         drm_framebuffer_cleanup(&rfb->base);
diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
index c578f265b24c..d1e595d91723 100644
--- a/drivers/gpu/drm/radeon/radeon_gem.c
+++ b/drivers/gpu/drm/radeon/radeon_gem.c
@@ -201,11 +201,11 @@ int radeon_gem_create_ioctl(struct drm_device *dev, void *data,
                 return r;
         }
         r = drm_gem_handle_create(filp, gobj, &handle);
+        /* drop reference from allocate - handle holds it now */
+        drm_gem_object_unreference_unlocked(gobj);
         if (r) {
-                drm_gem_object_unreference_unlocked(gobj);
                 return r;
         }
-        drm_gem_object_handle_unreference_unlocked(gobj);
         args->handle = handle;
         return 0;
 }
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 774e1d49509b..07e4726a4ee0 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -612,7 +612,7 @@ struct drm_gem_object {
         struct kref refcount;
 
         /** Handle count of this object. Each handle also holds a reference */
-        struct kref handlecount;
+        atomic_t handle_count; /* number of handles on this object */
 
         /** Related drm device */
         struct drm_device *dev;
@@ -1461,7 +1461,7 @@ struct drm_gem_object *drm_gem_object_alloc(struct drm_device *dev,
                                             size_t size);
 int drm_gem_object_init(struct drm_device *dev,
                         struct drm_gem_object *obj, size_t size);
-void drm_gem_object_handle_free(struct kref *kref);
+void drm_gem_object_handle_free(struct drm_gem_object *obj);
 void drm_gem_vm_open(struct vm_area_struct *vma);
 void drm_gem_vm_close(struct vm_area_struct *vma);
 int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma);
@@ -1496,7 +1496,7 @@ static inline void
 drm_gem_object_handle_reference(struct drm_gem_object *obj)
 {
         drm_gem_object_reference(obj);
-        kref_get(&obj->handlecount);
+        atomic_inc(&obj->handle_count);
 }
 
 static inline void
@@ -1505,12 +1505,15 @@ drm_gem_object_handle_unreference(struct drm_gem_object *obj)
         if (obj == NULL)
                 return;
 
+        if (atomic_read(&obj->handle_count) == 0)
+                return;
         /*
          * Must bump handle count first as this may be the last
          * ref, in which case the object would disappear before we
          * checked for a name
          */
-        kref_put(&obj->handlecount, drm_gem_object_handle_free);
+        if (atomic_dec_and_test(&obj->handle_count))
+                drm_gem_object_handle_free(obj);
         drm_gem_object_unreference(obj);
 }
 
@@ -1520,12 +1523,17 @@ drm_gem_object_handle_unreference_unlocked(struct drm_gem_object *obj)
         if (obj == NULL)
                 return;
 
+        if (atomic_read(&obj->handle_count) == 0)
+                return;
+
         /*
         * Must bump handle count first as this may be the last
         * ref, in which case the object would disappear before we
         * checked for a name
         */
-        kref_put(&obj->handlecount, drm_gem_object_handle_free);
+
+        if (atomic_dec_and_test(&obj->handle_count))
+                drm_gem_object_handle_free(obj);
         drm_gem_object_unreference_unlocked(obj);
 }