Linux Weekly News

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In a combined filesystem and storage session at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM), Chuck Lever wanted to discuss the need for a permanent, globally unique ID for network filesystems. He was joined by Hannes Reinecke who has worked on the problem for NVMe storage devices; Lever said something along those lines is needed for NFSv4. He was hoping to find a solution during the session, though it would seem that the solution may lie in user space—and documentation.

OpenSUSE Leap Micro is a new distribution, described as "an ultra-reliable, lightweight operating system built for containerized and virtualized workloads". The initial release (5.2) is now available. More information can be found in the 5.2 release notes.

A longstanding problem with Btrfs subvolumes and duplicate inode numbers was the topic of a late-breaking filesystem session at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM). The problem had cropped up in the bcachefs session but Josef Bacik deferred that discussion to this just-created session, which he led. The problem is not limited to Btrfs, though, since filesystem snapshots for other filesystems can have similar kinds of problems.

The 5.17.9, 5.15.41, 5.10.117, 5.4.195, 4.19.244, 4.14.280, and 4.9.315 stable kernel updates have all been released; each contains another set of important fixes.

Security updates have been issued by Debian (elog, needrestart, openssl, and waitress), Fedora (curl, libxml2, slurm, and vim), Scientific Linux (zlib), SUSE (e2fsprogs, nodejs10, php72, and thunderbird), and Ubuntu (apport, clamav, needrestart, and pcre3).

Bcachefs is a longstanding out-of-tree filesystem that grew out of the bcache caching layer that has been in the kernel for nearly ten years. Based on a session led by Kent Overstreet at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM), though, it would seem that bcachefs is likely to be heading upstream soon. He intends to start the process toward mainline inclusion over the next six months or so.

The Linux kernel allows processes to share pages in memory, but the page tables used to control that sharing are not, themselves, shared; as a result, processes sharing memory maintain duplicate copies of the page-table data. Normally this duplication imposes little overhead, but there are situations where it can hurt. At the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM), Khaled Aziz (remotely) and Matthew Wilcox led a session to discuss a proposed mechanism to allow those page tables to be shared between cooperating processes.

Version 1.2 of the Inkscape drawing tool has been released. New features include multi-page support, editable markers, the ability to flow text around shapes, and more; see the release notes for details.

Security updates have been issued by Debian (cifs-utils, ffmpeg, libxml2, and vim), Fedora (rsyslog), Mageia (chromium-browser-stable), SUSE (chromium, containerd, docker, e2fsprogs, gzip, jackson-databind, jackson-dataformats-binary, jackson-annotations, jackson-bom, jackson-core, kernel, nodejs8, openldap2, pidgin, podofo, slurm, and tiff), and Ubuntu (clamav, containerd, libxml2, and openldap).

It is perhaps unusual to have a kernel tracing developer leading a filesystem session, Steven Rostedt said, at the beginning of such a session at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM). But he was doing so to try to find a good way to dynamically allocate kernel data structures for some of the pseudo-filesystems, such as sysfs, debugfs, and tracefs, in the kernel. Avoiding static allocations would save memory, especially on systems that are not actually using any of the files in those filesystems.

Software Freedom Conservancy (SFC) has announced that it succeeded with its motion in US Federal Court to send the case back to California, where it was originally filed. The suit was filed in October 2021 by SFC, as an owner of Vizio televisions, to get the company to comply with the GPL on some of the code in the TVs. Back in November, Vizio had asked to move the case to Federal Court, because the GPL is only a copyright license (which is a dispute handled at the Federal level) and not a contract (that could be adjudicated in state court). Friday's ruling disagreed with that premise: The May 13 ruling by the Honorable Josephine L. Staton stated that the claim from Software Freedom Conservancy succeeded in the "extra element test" and was not preempted by copyright claims, and the court finds "that the enforcement of 'an additional contractual promise separate and distinct from any rights provided by the copyright laws' amounts to an 'extra element,' and therefore, SFC's claims are not preempted."

"The ruling is a watershed moment in the history of copyleft licensing. This ruling shows that the GPL agreements function both as copyright licenses and as contractual agreements," says Karen M. Sandler, executive director of Software Freedom Conservancy. Sandler noted that many in the Free and Open Source Software (FOSS) legal community argue incorrectly that the GPL and other copyleft licenses only function as copyright licenses.

A new helper library for network filesystems, called netfslib, was the subject of a filesystem session at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM). David Howells developed netfslib, which was merged for 5.13 a year ago, and led the session. Some filesystems, like AFS and Ceph, are already using some of the services that netfslib provides, while others are starting to look into it.

Security updates have been issued by CentOS (gzip, java-1.8.0-openjdk, java-11-openjdk, and zlib), Debian (adminer, htmldoc, imagemagick, libgoogle-gson-java, lrzip, openjdk-8, openssl, and ruby-nokogiri), Fedora (ecdsautils, et, libxml2, podman, and supertux), Mageia (cairo, clamav, curl, fish, freetype2, golang-github-prometheus-client, python-django-registration, python-nbxmpp, python-waitress, and xmlrpc-c), Red Hat (pcs), SUSE (curl, kernel, pidgin, and webkit2gtk3), and Ubuntu (tiff).

The 5.18-rc7 kernel prepatch has been released for testing. Linus says: "So things continue to be fairly calm, and as such this is likely the last rc before 5.18 unless something bad happens next week".

The 5.17.8, 5.15.40, 5.10.116, 5.4.194, 4.19.243, 4.14.279, and 4.9.314 stable kernels have been released; each contains another set of important fixes.

Memory reclaim in Linux is largely a reactive practice; the kernel tries to find memory it can repurpose in response to the amount of free memory falling too low. Developers have often wondered if a proactive reclaim mechanism might lead to better performance, for some workloads at least, and optimal use of tiered-memory systems will likely require more active reclamation of memory as well. At the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM), Davidlohr Bueso led a brief session on the topic.

Compute Express Link (CXL) is an upcoming memory technology that is clearly on the minds of Linux memory-management developers; there were five sessions dedicated to the topic at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM). The first three sessions, on May 3, covered various aspects of memory management in the presence of CXL. It seems that CXL may bring some welcome capabilities, especially for cloud-service providers, but that will come at the cost of some headaches on the kernel-development side.

Security updates have been issued by Debian (chromium, postgresql-11, postgresql-13, and waitress), Fedora (curl, java-1.8.0-openjdk-aarch32, keylime, and pcre2), Oracle (gzip and zlib), Red Hat (subversion:1.10), SUSE (clamav, documentation-suse-openstack-cloud, kibana, openstack-keystone, openstack-monasca-notification, e2fsprogs, gzip, and kernel), and Ubuntu (libvorbis and rsyslog).

Many types of kernel changes can be hammered into shape on the mailing lists. There are certain types of patches, however, that have a hard time getting to the finish line that way; they are sufficiently large and invasive that they need an actual gathering of the developers involved. The multi-generational LRU work (MGLRU) falls into this category, which is why it was the subject of a full-hour session at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM). The discussion held there may well have opened the doors for this code to be merged in the near future.