Subject: bug#589: This version introduce btrfs free cache incompatibility

From: Klaus Ethgen <[email-masked]>
Date: Sat, 3 Jul 2021 22:21:42 +0100

Package: linux-image-4.9.0-16-686-pae
Version: 4.9.272-1
Severity: critical

This release introduce introduce an incompatibility in btrfs free space
cache which leads to an filesystem corruption!

The solution is simple but not obvious: Do a `mount -o
remount,clear_cache,space_cache /filesystem` as early as possible after
boot into the new kernel for every btrfs filesystem.

Please add a release note and a warning for the admin.

-- System Information:
Distributor ID:	Devuan
Description:	Devuan GNU/Linux 4 (chimaera)
Release:	4
Codename:	n/a
Architecture: x86_64

Kernel: Linux 5.10.21 (SMP w/8 CPU threads)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_FIRMWARE_WORKAROUND, TAINT_OOT_MODULE
Locale: LANG=C, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)
-- 
Klaus Ethgen                                       http://www.ethgen.ch/
pub  4096R/4E20AF1C 2011-05-16            Klaus Ethgen <[email-masked]>
Fingerprint: 85D4 CA42 952C 949B 1753  62B3 79D0 B06F 4E20 AF1C