Please add 848c23b78fafdcd3270b to 4.9.x

Hi,

please add commit 848c23b78fafdcd3270b ("btrfs: Remove false alert when fiemap range is smaller than on-disk extent") to the 4.9.x stable tree. It fixes a (harmless) warning but that's causing noise and false alerts, we got a user report.

The warning was introduced by backport to v4.9.136 (commit id in stable tree is 4b1cfa2e9db6168bcbcc). No other stable trees are affected.

The patch applies cleanly on 4.9.158.

Thanks.