The "extent tree (at level 1) could be narrower" message is
overly verbose and raises concerns by end users, even though
it is harmless. On the flip side, this may save only a few
hundred blocks in the filesystem for a short period of time,
so there is little benefit to be had by printing a message.
Disable the extent optimization step in e2fsck by default by
adding the "no_optimize_extents" option to e2fsck.conf.
diff --git a/e2fsck.conf b/e2fsck.conf
new file mode 100644
index 000000000..b774f9ebf
--- /dev/null
+++ b/e2fsck.conf
@@ -0,0 +1,3 @@
+[options]
+# disable extent optimization to avoid spurios "errors" during runs
+no_optimize_extents=true
