1. Please describe the problem: zram has a feature where it can writeback to a backing device, this is useful for people who want to use zram but still have the advantage of writeback capability of zswap. My Arch setup for example, uses a swapfile attached as a loop device (because zram backing dev only support devices rn not files), and a systemd timer unit that triggers writeback activity. 2. What is the Version-Release number of the kernel: 6.10.3-200.fc40.x86_64 3. Did it work previously in Fedora? If so, what kernel version did the issue *first* appear? Old kernels are available for download at https://koji.fedoraproject.org/koji/packageinfo?packageID=8 : No 4. Can you reproduce this issue? If so, please provide the steps to reproduce the issue below: - create a zram device - check if /sys/block/zramX/{backing_dev,writeback} exist - it does not = CONFIG_ZRAM_WRITEBACK is not applied 5. Does this problem occur with the latest Rawhide kernel? To install the Rawhide kernel, run ``sudo dnf install fedora-repos-rawhide`` followed by ``sudo dnf update --enablerepo=rawhide kernel``: No 6. Are you running any modules that not shipped with directly Fedora's kernel?: No 7. Please attach the kernel logs. You can get the complete kernel log for a boot with ``journalctl --no-hostname -k > dmesg.txt``. If the issue occurred on a previous boot, use the journalctl ``-b`` flag. not really needed, so here's proof the kernel isn't built with the support instead ``` cat /usr/lib/modules/6.11.0-0.rc3.20240814git6b0f8db921ab.32.fc42.x86_64/config | grep CONFIG_ZRAM_WRITEBACK # CONFIG_ZRAM_WRITEBACK is not set ``` Reproducible: Always
I think it would be highly beneficial to enable this feature, as it has already been present in the kernel since 2013. Its use is still optional, so everyone can decide for themselves whether and how to use it or not. The question of data security simply has to be answered by each user. Writing kernel pages to a block device can certainly expose sensitive data. Thank you for taking this into consideration and for your efforts in relation to this feature.
FEDORA-2024-b8b5224019 (kernel-6.11.3-300.fc41 and kernel-headers-6.11.3-300.fc41) has been submitted as an update to Fedora 41. https://bodhi.fedoraproject.org/updates/FEDORA-2024-b8b5224019
FEDORA-2024-b8b5224019 has been pushed to the Fedora 41 testing repository. Soon you'll be able to install the update with the following command: `sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2024-b8b5224019` You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2024-b8b5224019 See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.
FEDORA-2024-b8b5224019 (kernel-6.11.3-300.fc41 and kernel-headers-6.11.3-300.fc41) has been pushed to the Fedora 41 stable repository. If problem still persists, please make note of it in this bug report.