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The final session in the memory-management track at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM) was run remotely by James Gowans and David Woodhouse. It was titled "user-space control of memory mappings", with a subtitle of "letting guest memory and state survive kexec". Some options were discussed, but the real work is clearly yet to be done.

As the memory-management track at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM) neared its conclusion, Mike Kravetz ran a session remotely to talk about page sharing with hugetlbfs, which is a special filesystem that provides access to huge pages. (See this article series for lots of information about hugetlbfs). Hugetlbfs can help to reduce page-table overhead when pages are shared between large numbers of processes, but there is a problem that he is trying to find a solution for.

The numerous correctness problems with the kernel's get_user_pages() functionality have been a fixture at the Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM) for some years. The 2022 event did not break that tradition. The first-day discussion on page pinning was covered here. On the final day, in the memory-management track, David Hildenbrand led a session on the current status of get_user_pages() and its interaction with copy-on-write (COW) memory.

Security updates have been issued by CentOS (kernel), Debian (ark, openldap, and thunderbird), Fedora (freetype and vim), Oracle (.NET 5.0, .NET 6.0, .NET Core 3.1, container-tools:3.0, glibc, kernel, rsync, and subversion:1.10), Scientific Linux (kernel), SUSE (dcraw, firefox, glib2, ImageMagick, kernel-firmware, libxml2, libyajl, php7, ucode-intel, and unrar), and Ubuntu (openldap).

Linux Plumbers Conference 2022 is pleased to host the linux/arch Microconference

The linux/arch microconference aims to bring architecture maintainers in one room to discuss how the code in arch/ can be improved, consolidated and generalized.

Potential topics for the discussion are:

• reducing code duplication and generalizing the common code in arch/
• making headers in include/asm consistent
• on-boarding more architectures to use common entry code
• devicetree (unless they have their own microconf)
• identifying old machine support that may be either still in
• active use vs only in hobbyist/retro-computing vs completely obsolete and broken

Please come and join us in the discussion about improving architectures integration with generic kernel code!

We hope to see you there!

Version 1.61.0 of the Rust language has been released. Changes this time around include more flexibility in main-program exit codes, a number of new features for const functions, a number of newly stabilized APIs, and more.

Control groups are a useful system-management feature, but they can also consume a lot of resources, especially if they hang around on the system after they have been deleted. Roman Gushchin described the problems that can result at the 2019 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM); he returned during the 2022 LSFMM to revisit the issue, especially as it relates to the memory controller. Progress has been made, but the problem is not yet solved.

During the final day of the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM), attention in the memory-management track turned once again to the challenges posed by the upcoming Compute Express Link (CXL) technology. Two sessions looked at different problems posed by CXL memory, which can come and go over the operation of the system. CXL offers a lot of flexibility, but changes will be needed for the kernel to be able to take advantage of it.

Andrew 'bunnie' Huang has posted an extensive review of the Rust language derived from the experience of writing "over 100k lines" of code.

Rust is a difficult language for authoring code because it makes these "cheats" hard – as long as you have the discipline of not using "unsafe" constructions to make cheats easy. However, really hard does not mean impossible – there were definitely some cheats that got swept under the rug during the construction of Xous.

This is where Rust really exceeded expectations for me. The language's structure and tooling was very good at hunting down these cheats and refactoring the code base, thus curing the cancer without killing the patient, so to speak. This is the point at which Rust’s very strict typing and borrow checker converts from a productivity liability into a productivity asset.

Security updates have been issued by Fedora (microcode_ctl, rubygem-nokogiri, and vim), Mageia (htmldoc, python-django, and python-oslo-utils), Red Hat (container-tools:2.0, kernel, kernel-rt, kpatch-patch, and pcs), SUSE (ardana-barbican, grafana, openstack-barbican, openstack-cinder, openstack-heat-gbp, openstack-horizon-plugin-gbp-ui, openstack-ironic, openstack-keystone, openstack-neutron-gbp, python-lxml, release-notes-suse-openstack-cloud, autotrace, curl, firefox, libslirp, php7, poppler, slurm_20_11, and ucode-intel), and Ubuntu (bind9, gnome-control-center, and libxrandr).

The LWN.net Weekly Edition for May 19, 2022 is available.

LWN does its best to provide comprehensive coverage of the free-software development community, but there is far more going on than our small staff can handle. When expressed that way, this problem suggests an obvious solution: make the staff bigger. Thus, LWN is looking to hire a writer/editor.

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.

Linux Plumbers Conference 2022 is pleased to host the Confidential Computing Microconference.

The Confidential Computing Microconference brings together plumbers enabling secure execution features in hypervisors, firmware, Linux Kernel, over low-level user space up to container runtimes.

Good progress was made on a couple of topics since the last year, but enabling Confidential Computing in the Linux ecosystem is an ongoing process, and there are still many problems to solve. The most important ones are:

• Design and implementation of Intel TDX and AMD SEV-SNP host support
• Linux kernel memory management changes for secure execution environments
• Support of upcoming secure execution hardware extensions from ARM and RISC-V
• Pre-launch and runtime attestation workflows
• Interrupt security for AMD SEV-SNP
• Debuggability and live migration of encrypted virtual machines
• Proper testing of confidential computing support code

Please come and join us in the discussion for solutions to the open problems for supporting these technologies!

We hope to see you there!

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.