Subject: zvol sync/flush regression in 2.2.7+
Package: zfs-dkms
X-Debbugs-Cc: f.gruenbichler@proxmox.com
Version: 2.2.7-1
Severity: grave
Forwarded: https://github.com/openzfs/zfs/pull/17131
Tags: upstream patch

hi!

zfs 2.2.7 and later do not honor all kinds of sync writes/flush requests properly when issued on zvols. notably, using a zvol as backing device
for a Qemu virtual block device is affected, and ZFS treats all sync
writes issued by applications in the VM as async. this can lead to inconsistencies or dataloss.

I bisected and found the upstream commit introducing the regression, and proposed a fix upstream (see linked PR, which also contains a reproducer).

the packages in trixie and bookworm-backports should probably both be
updated, the fix is rather small and targeted ;)

thanks for your consideration!
Fabian

-- System Information:
Debian Release: trixie/sid
APT prefers unstable
APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: arm64

Kernel: Linux 6.12.17-amd64 (SMP w/8 CPU threads; PREEMPT)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages zfs-dkms depends on:
ii debconf [debconf-2.0] 1.5.91
ii dkms 3.1.5-1
ii file 1:5.45-3+b1
ii libc6-dev [libc-dev] 2.41-4
ii libpython3-stdlib 3.13.2-2
ii lsb-release 12.1-1

Versions of packages zfs-dkms recommends:
ii linux-libc-dev 6.12.17-1
ii zfs-zed 2.3.0-2
ii zfsutils-linux 2.3.0-2

Versions of packages zfs-dkms suggests:
ii debhelper 13.24.1

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