CVE-2026-31666 btrfs: fix incorrect return value after changing leaf in lookup_extent_data_ref()

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix incorrect return value after changing leaf in lookupextentdataref After commit 1618aa3c2e01 "btrfs: simplify return variables in lookupextentdataref", the err and ret variables were merged into a single ret variable...