glamor: Prepare/finish access once if src equal to dst.

Signed-off-by: Zhigang Gong <zhigang.gong@linux.intel.com>

glamor/glamor_copyarea.c

@@ -322,6 +322,7 @@ glamor_copy_n_to_n(DrawablePtr src,
         goto done;
 	return;
     }
+
     glamor_report_delayed_fallbacks(src->pScreen);
     glamor_report_delayed_fallbacks(dst->pScreen);
 
@@ -329,11 +330,12 @@ glamor_copy_n_to_n(DrawablePtr src,
 		    glamor_get_drawable_location(src),
 		    glamor_get_drawable_location(dst));
     if (glamor_prepare_access(dst, GLAMOR_ACCESS_RW)) {
-	if (glamor_prepare_access(src, GLAMOR_ACCESS_RO)) {
+	if (dst == src || glamor_prepare_access(src, GLAMOR_ACCESS_RO)) {
 	    fbCopyNtoN(src, dst, gc, box, nbox,
 		       dx, dy, reverse, upsidedown, bitplane,
 		       closure);
-	    glamor_finish_access(src);
+            if (dst != src)
+	      glamor_finish_access(src);
 	}
 	glamor_finish_access(dst);
     }