drm/i915: Keep refs on the object over the lifetime of vmas for GTT mmap.

This fixes potential fault at fault time if the object was unreferenced
while the mapping still existed.  Now, while the mmap_offset only lives
for the lifetime of the object, the object also stays alive while a vma
exists that needs it.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

4 files changed, 57 insertions, 18 deletions

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 5dad6b9d0dec..88d3368ffddd 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -463,6 +463,26 @@ drm_gem_object_handle_free(struct kref *kref)
 }
 EXPORT_SYMBOL(drm_gem_object_handle_free);
 
+void drm_gem_vm_open(struct vm_area_struct *vma)
+{
+	struct drm_gem_object *obj = vma->vm_private_data;
+
+	drm_gem_object_reference(obj);
+}
+EXPORT_SYMBOL(drm_gem_vm_open);
+
+void drm_gem_vm_close(struct vm_area_struct *vma)
+{
+	struct drm_gem_object *obj = vma->vm_private_data;
+	struct drm_device *dev = obj->dev;
+
+	mutex_lock(&dev->struct_mutex);
+	drm_gem_object_unreference(obj);
+	mutex_unlock(&dev->struct_mutex);
+}
+EXPORT_SYMBOL(drm_gem_vm_close);
+
+
 /**
  * drm_gem_mmap - memory map routine for GEM objects
  * @filp: DRM file pointer
@@ -524,6 +544,14 @@ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
 #endif
 	vma->vm_page_prot = __pgprot(prot);
 
+	/* Take a ref for this mapping of the object, so that the fault
+	 * handler can dereference the mmap offset's pointer to the object.
+	 * This reference is cleaned up by the corresponding vm_close
+	 * (which should happen whether the vma was created by this call, or
+	 * by a vm_open due to mremap or partial unmap or whatever).
+	 */
+	drm_gem_object_reference(obj);
+
 	vma->vm_file = filp;	/* Needed for drm_vm_open() */
 	drm_vm_open_locked(vma);
 
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index aac12ee31a46..a31cbdbc3c54 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -94,6 +94,8 @@ static int i915_resume(struct drm_device *dev)
 
 static struct vm_operations_struct i915_gem_vm_ops = {
 	.fault = i915_gem_fault,
+	.open = drm_gem_vm_open,
+	.close = drm_gem_vm_close,
 };
 
 static struct drm_driver driver = {
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 078858178832..ac534c9a2f81 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -607,8 +607,6 @@ int i915_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	case -EAGAIN:
 		return VM_FAULT_OOM;
 	case -EFAULT:
-	case -EBUSY:
-		DRM_ERROR("can't insert pfn??  fault or busy...\n");
 		return VM_FAULT_SIGBUS;
 	default:
 		return VM_FAULT_NOPAGE;
@@ -684,6 +682,30 @@ out_free_list:
 	return ret;
 }
 
+static void
+i915_gem_free_mmap_offset(struct drm_gem_object *obj)
+{
+	struct drm_device *dev = obj->dev;
+	struct drm_i915_gem_object *obj_priv = obj->driver_private;
+	struct drm_gem_mm *mm = dev->mm_private;
+	struct drm_map_list *list;
+
+	list = &obj->map_list;
+	drm_ht_remove_item(&mm->offset_hash, &list->hash);
+
+	if (list->file_offset_node) {
+		drm_mm_put_block(list->file_offset_node);
+		list->file_offset_node = NULL;
+	}
+
+	if (list->map) {
+		drm_free(list->map, sizeof(struct drm_map), DRM_MEM_DRIVER);
+		list->map = NULL;
+	}
+
+	obj_priv->mmap_offset = 0;
+}
+
 /**
  * i915_gem_get_gtt_alignment - return required GTT alignment for an object
  * @obj: object to check
@@ -2896,9 +2918,6 @@ int i915_gem_init_object(struct drm_gem_object *obj)
 void i915_gem_free_object(struct drm_gem_object *obj)
 {
 	struct drm_device *dev = obj->dev;
-	struct drm_gem_mm *mm = dev->mm_private;
-	struct drm_map_list *list;
-	struct drm_map *map;
 	struct drm_i915_gem_object *obj_priv = obj->driver_private;
 
 	while (obj_priv->pin_count > 0)
@@ -2909,19 +2928,7 @@ void i915_gem_free_object(struct drm_gem_object *obj)
 
 	i915_gem_object_unbind(obj);
 
-	list = &obj->map_list;
-	drm_ht_remove_item(&mm->offset_hash, &list->hash);
-
-	if (list->file_offset_node) {
-		drm_mm_put_block(list->file_offset_node);
-		list->file_offset_node = NULL;
-	}
-
-	map = list->map;
-	if (map) {
-		drm_free(map, sizeof(*map), DRM_MEM_DRIVER);
-		list->map = NULL;
-	}
+	i915_gem_free_mmap_offset(obj);
 
 	drm_free(obj_priv->page_cpu_valid, 1, DRM_MEM_DRIVER);
 	drm_free(obj->driver_private, 1, DRM_MEM_DRIVER);
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 8190b9bcc2d9..e5f4ae989abf 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1321,6 +1321,8 @@ void drm_gem_object_free(struct kref *kref);
 struct drm_gem_object *drm_gem_object_alloc(struct drm_device *dev,
 					    size_t size);
 void drm_gem_object_handle_free(struct kref *kref);
+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);
 
 static inline void