drm/i915: Refactor testing obj->mm.pages

Since we occasionally stuff an error pointer into obj->mm.pages for a
semi-permanent or even permanent failure, we have to be more careful and
not just test against NULL when deciding if the object has a complete
set of its concurrent pages.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171013202621.7276-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_drv.h

@@ -3566,10 +3566,16 @@ i915_gem_object_pin_pages(struct drm_i915_gem_object *obj)
 	return __i915_gem_object_get_pages(obj);
 }
 
+static inline bool
+i915_gem_object_has_pages(struct drm_i915_gem_object *obj)
+{
+	return !IS_ERR_OR_NULL(READ_ONCE(obj->mm.pages));
+}
+
 static inline void
 __i915_gem_object_pin_pages(struct drm_i915_gem_object *obj)
 {
-	GEM_BUG_ON(!obj->mm.pages);
+	GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 
 	atomic_inc(&obj->mm.pages_pin_count);
 }
@@ -3583,8 +3589,8 @@ i915_gem_object_has_pinned_pages(struct drm_i915_gem_object *obj)
 static inline void
 __i915_gem_object_unpin_pages(struct drm_i915_gem_object *obj)
 {
+	GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
-	GEM_BUG_ON(!obj->mm.pages);
 
 	atomic_dec(&obj->mm.pages_pin_count);
 }

drivers/gpu/drm/i915/i915_gem.c

@@ -2196,7 +2196,7 @@ void __i915_gem_object_invalidate(struct drm_i915_gem_object *obj)
 	struct address_space *mapping;
 
 	lockdep_assert_held(&obj->mm.lock);
-	GEM_BUG_ON(obj->mm.pages);
+	GEM_BUG_ON(i915_gem_object_has_pages(obj));
 
 	switch (obj->mm.madv) {
 	case I915_MADV_DONTNEED:
@@ -2259,7 +2259,7 @@ void __i915_gem_object_put_pages(struct drm_i915_gem_object *obj,
 		return;
 
 	GEM_BUG_ON(obj->bind_count);
-	if (!READ_ONCE(obj->mm.pages))
+	if (!i915_gem_object_has_pages(obj))
 		return;
 
 	/* May be called by shrinker from within get_pages() (on another bo) */
@@ -2563,7 +2563,7 @@ int __i915_gem_object_get_pages(struct drm_i915_gem_object *obj)
 	if (err)
 		return err;
 
-	if (unlikely(IS_ERR_OR_NULL(obj->mm.pages))) {
+	if (unlikely(!i915_gem_object_has_pages(obj))) {
 		GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
 
 		err = ____i915_gem_object_get_pages(obj);
@@ -2648,7 +2648,7 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 	type &= ~I915_MAP_OVERRIDE;
 
 	if (!atomic_inc_not_zero(&obj->mm.pages_pin_count)) {
-		if (unlikely(IS_ERR_OR_NULL(obj->mm.pages))) {
+		if (unlikely(!i915_gem_object_has_pages(obj))) {
 			GEM_BUG_ON(i915_gem_object_has_pinned_pages(obj));
 
 			ret = ____i915_gem_object_get_pages(obj);
@@ -2660,7 +2660,7 @@ void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
 		atomic_inc(&obj->mm.pages_pin_count);
 		pinned = false;
 	}
-	GEM_BUG_ON(!obj->mm.pages);
+	GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 
 	ptr = page_unpack_bits(obj->mm.mapping, &has_type);
 	if (ptr && has_type != type) {
@@ -2715,7 +2715,7 @@ i915_gem_object_pwrite_gtt(struct drm_i915_gem_object *obj,
 	 * allows it to avoid the cost of retrieving a page (either swapin
 	 * or clearing-before-use) before it is overwritten.
 	 */
-	if (READ_ONCE(obj->mm.pages))
+	if (i915_gem_object_has_pages(obj))
 		return -ENODEV;
 
 	/* Before the pages are instantiated the object is treated as being
@@ -4278,7 +4278,7 @@ i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
 	if (err)
 		goto out;
 
-	if (obj->mm.pages &&
+	if (i915_gem_object_has_pages(obj) &&
 	    i915_gem_object_is_tiled(obj) &&
 	    dev_priv->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
 		if (obj->mm.madv == I915_MADV_WILLNEED) {
@@ -4297,7 +4297,8 @@ i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
 		obj->mm.madv = args->madv;
 
 	/* if the object is no longer attached, discard its backing storage */
-	if (obj->mm.madv == I915_MADV_DONTNEED && !obj->mm.pages)
+	if (obj->mm.madv == I915_MADV_DONTNEED &&
+	    !i915_gem_object_has_pages(obj))
 		i915_gem_object_truncate(obj);
 
 	args->retained = obj->mm.madv != __I915_MADV_PURGED;
@@ -4514,7 +4515,7 @@ static void __i915_gem_free_objects(struct drm_i915_private *i915,
 		if (WARN_ON(i915_gem_object_has_pinned_pages(obj)))
 			atomic_set(&obj->mm.pages_pin_count, 0);
 		__i915_gem_object_put_pages(obj, I915_MM_NORMAL);
-		GEM_BUG_ON(obj->mm.pages);
+		GEM_BUG_ON(i915_gem_object_has_pages(obj));
 
 		if (obj->base.import_attach)
 			drm_prime_gem_destroy(&obj->base, NULL);

drivers/gpu/drm/i915/i915_gem_clflush.c

@@ -70,6 +70,7 @@ static const struct dma_fence_ops i915_clflush_ops = {
 
 static void __i915_do_clflush(struct drm_i915_gem_object *obj)
 {
+	GEM_BUG_ON(!i915_gem_object_has_pages(obj));
 	drm_clflush_sg(obj->mm.pages);
 	intel_fb_obj_flush(obj, ORIGIN_CPU);
 }

drivers/gpu/drm/i915/i915_gem_render_state.c

@@ -229,7 +229,7 @@ int i915_gem_render_state_emit(struct drm_i915_gem_request *req)
 		return 0;
 
 	/* Recreate the page after shrinking */
-	if (!so->vma->obj->mm.pages)
+	if (!i915_gem_object_has_pages(so->vma->obj))
 		so->batch_offset = -1;
 
 	ret = i915_vma_pin(so->vma, 0, 0, PIN_GLOBAL | PIN_HIGH);

drivers/gpu/drm/i915/i915_gem_shrinker.c

@@ -97,7 +97,7 @@ static bool swap_available(void)
 
 static bool can_release_pages(struct drm_i915_gem_object *obj)
 {
-	if (!obj->mm.pages)
+	if (!i915_gem_object_has_pages(obj))
 		return false;
 
 	/* Consider only shrinkable ojects. */
@@ -129,7 +129,7 @@ static bool unsafe_drop_pages(struct drm_i915_gem_object *obj)
 {
 	if (i915_gem_object_unbind(obj) == 0)
 		__i915_gem_object_put_pages(obj, I915_MM_SHRINKER);
-	return !READ_ONCE(obj->mm.pages);
+	return !i915_gem_object_has_pages(obj);
 }
 
 /**
@@ -247,7 +247,7 @@ i915_gem_shrink(struct drm_i915_private *dev_priv,
 				/* May arrive from get_pages on another bo */
 				mutex_lock_nested(&obj->mm.lock,
 						  I915_MM_SHRINKER);
-				if (!obj->mm.pages) {
+				if (!i915_gem_object_has_pages(obj)) {
 					__i915_gem_object_invalidate(obj);
 					list_del_init(&obj->global_link);
 					count += obj->base.size >> PAGE_SHIFT;
@@ -413,7 +413,7 @@ i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 	 */
 	unbound = bound = unevictable = 0;
 	list_for_each_entry(obj, &dev_priv->mm.unbound_list, global_link) {
-		if (!obj->mm.pages)
+		if (!i915_gem_object_has_pages(obj))
 			continue;
 
 		if (!can_release_pages(obj))
@@ -422,7 +422,7 @@ i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 			unbound += obj->base.size >> PAGE_SHIFT;
 	}
 	list_for_each_entry(obj, &dev_priv->mm.bound_list, global_link) {
-		if (!obj->mm.pages)
+		if (!i915_gem_object_has_pages(obj))
 			continue;
 
 		if (!can_release_pages(obj))

drivers/gpu/drm/i915/i915_gem_tiling.c

@@ -269,7 +269,7 @@ i915_gem_object_set_tiling(struct drm_i915_gem_object *obj,
 	 * due to the change in swizzling.
 	 */
 	mutex_lock(&obj->mm.lock);
-	if (obj->mm.pages &&
+	if (i915_gem_object_has_pages(obj) &&
 	    obj->mm.madv == I915_MADV_WILLNEED &&
 	    i915->quirks & QUIRK_PIN_SWIZZLED_PAGES) {
 		if (tiling == I915_TILING_NONE) {

drivers/gpu/drm/i915/i915_gem_userptr.c

@@ -82,7 +82,7 @@ static void cancel_userptr(struct work_struct *work)
 	/* We are inside a kthread context and can't be interrupted */
 	if (i915_gem_object_unbind(obj) == 0)
 		__i915_gem_object_put_pages(obj, I915_MM_NORMAL);
-	WARN_ONCE(obj->mm.pages,
+	WARN_ONCE(i915_gem_object_has_pages(obj),
 		  "Failed to release pages: bind_count=%d, pages_pin_count=%d, pin_display=%d\n",
 		  obj->bind_count,
 		  atomic_read(&obj->mm.pages_pin_count),