drm/i915: Unwind vma->pages allocation upon failure

If we fail to allocate the ppgtt range after allocating the pages for
the vma, we should unwind the local allocation before reporting back the
failure.

Fixes: ff685975d97f ("drm/i915: Move allocate_va_range to GTT")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170227122654.27651-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -2312,7 +2312,7 @@ static int aliasing_gtt_bind_vma(struct i915_vma *vma,
 							     vma->node.start,
 							     vma->node.size);
 			if (ret)
-				return ret;
+				goto err_pages;
 		}
 
 		appgtt->base.insert_entries(&appgtt->base,
@@ -2329,6 +2329,17 @@ static int aliasing_gtt_bind_vma(struct i915_vma *vma,
 	}
 
 	return 0;
+
+err_pages:
+	if (!(vma->flags & (I915_VMA_GLOBAL_BIND | I915_VMA_LOCAL_BIND))) {
+		if (vma->pages != vma->obj->mm.pages) {
+			GEM_BUG_ON(!vma->pages);
+			sg_free_table(vma->pages);
+			kfree(vma->pages);
+		}
+		vma->pages = NULL;
+	}
+	return ret;
 }
 
 static void aliasing_gtt_unbind_vma(struct i915_vma *vma)