drm: pre allocate node for create_block

For an upcoming patch where we introduce the i915 VMA, it's ideal to
have the drm_mm_node as part of the VMA struct (ie. it's pre-allocated).
Part of the conversion to VMAs is to kill off obj->gtt_space. Doing this
will break a bunch of code, but amongst them are 2 callers of
drm_mm_create_block(), both related to stolen memory.

It also allows us to embed the drm_mm_node into the object currently
which provides a nice transition over to the new code.

v2: Reordered to do before ripping out obj->gtt_offset.
Some minor cleanups made available because of reordering.

v3: s/continue/break on failed stolen node allocation (David)
Set obj->gtt_space on failed node allocation (David)
Only unref stolen (fix double free) on failed create_stolen (David)
Free node, and NULL it in failed create_stolen (David)
Add back accidentally removed newline (David)

CC: <dri-devel@lists.freedesktop.org>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Acked-by: David Airlie <airlied@linux.ie>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index 07cf99c..9e8dfbc 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -147,12 +147,10 @@
 	}
 }
 
-struct drm_mm_node *drm_mm_create_block(struct drm_mm *mm,
-					unsigned long start,
-					unsigned long size,
-					bool atomic)
+int drm_mm_create_block(struct drm_mm *mm, struct drm_mm_node *node,
+			unsigned long start, unsigned long size)
 {
-	struct drm_mm_node *hole, *node;
+	struct drm_mm_node *hole;
 	unsigned long end = start + size;
 	unsigned long hole_start;
 	unsigned long hole_end;
@@ -161,10 +159,6 @@
 		if (hole_start > start || hole_end < end)
 			continue;
 
-		node = drm_mm_kmalloc(mm, atomic);
-		if (unlikely(node == NULL))
-			return NULL;
-
 		node->start = start;
 		node->size = size;
 		node->mm = mm;
@@ -184,11 +178,11 @@
 			node->hole_follows = 1;
 		}
 
-		return node;
+		return 0;
 	}
 
 	WARN(1, "no hole found for block 0x%lx + 0x%lx\n", start, size);
-	return NULL;
+	return -ENOSPC;
 }
 EXPORT_SYMBOL(drm_mm_create_block);