Regression in 4.14.147, 4.19.76, 5.2.18 leading to kernel panic on btrfs root fs mount

[Andrew Macks]

Was not sure the correct way to escalate this quickly enough.  I
unfortunately discovered this issue while upgrading a server (remotely) to
4.19.78 (longterm).

*Bug 205181* <https://bugzilla.kernel.org/show_bug.cgi?id=205181> - kernel
panic when accessing btrfs root device with f2fs in kernel
https://bugzilla.kernel.org/show_bug.cgi?id=205181

Andrew.