Watch Out For BCache Corruption Issues On Linux 5.0 & GCC 9
It appears that those employing BCache and running Linux 5.0 or newer when built by GCC 9, there is a nasty corruption bug exposed.
Multiple users are confirming "massive filesystem corruption" including by the stock Fedora 30 kernel which is built by GCC9 and based on Linux 5.0. There is also this related Red Hat bug entry.
The issue doesn't appear to be Fedora-specific but rather they are one of the first distributions on the Linux 5.0 + GCC 9 combination. Fedora is looking at warning users trying to upgrade if they are making use of BCache as "any bcache user upgrading to Fedora30 involuntarily corrupts his storage."
Hopefully this bug will be resolved soon now that there is added attention and urgency, stay tuned.