Two different topics concerning the virtual filesystem (VFS) layer were the subject of a session led by VFS co-maintainer Christian Brauner at the 2023 Linux Storage, Filesystem, Memory-Management and BPF Summit. As might be guessed, it was a filesystem-track session; Brauner had three separate items he planned on bringing up, but the discussion on the first two consumed the whole half-hour—and then some. A mechanism to avoid media-change races when mounting loop (or loopback) and other devices was disposed of fairly quickly, but the discussion around the mount-beneath feature went on at length.

Priority inversion comes about when a low-priority task holds a resource that is needed by a higher-priority task, with the result that the wrong task is the only one that can run. This problem is arguably most acute in realtime settings, but it can happen in just about any system that has multiple tasks running. The variety of scheduling classes provided by the Linux kernel make handling priority inversion a difficult problem; the latest version of the proxy execution patch series points toward a possible solution.

Greg Kroah-Hartman has released the 6.3.7, 6.1.33, 5.15.116, 5.10.183, 5.4.246, 4.19.285, and 4.14.317 stable kernels. As usual, they contain many important fixes throughout the tree; users of those series should upgrade.

Security updates have been issued by Debian (jupyter-core, openssl, and ruby2.5), Fedora (firefox), Mageia (libreoffice, openssl, and python-flask), Red Hat (python and python3), Slackware (mozilla, php8, and python3), SUSE (java-1_8_0-ibm, libcares2, mariadb, and python36), and Ubuntu (linux, linux-aws, linux-kvm, linux-lts-xenial, linux-gke, linux-intel-iotg, linux-raspi, linux-xilinx-zynqmp, and mozjs102).

The kernel is an increasingly dynamic body of code, where new executable text can show up at any time. Currently, the task of allocating memory for new kernel code falls on the subsystem that first brought the ability to load code into a running kernel: the module loader. This patch set from Mike Rapoport looks to move the responsibility for these allocations to a new "JIT allocator", addressing a number of rough edges in the process.

Security updates have been issued by Debian (chromium, firefox-esr, and ruby2.5), Fedora (curl, dbus, pypy, pypy3.8, pypy3.9, python3.10, and python3.8), Red Hat (python and python-flask), Scientific Linux (emacs), SUSE (firefox, google-cloud-sap-agent, libwebp, opensc, openssl, openssl-3, openssl1, python-sqlparse, python310, and supportutils), and Ubuntu (libxml2, netatalk, and sysstat).

The LWN.net Weekly Edition for June 8, 2023 is available.

Gao Xiang gave an overview of the Extended Read-Only File System (EROFS) in a filesystem session at the 2023 Linux Storage, Filesystem, Memory-Management and BPF Summit. EROFS was added to Linux 5.4 in 2019 and has been increasingly used in places beyond its roots as a filesystem for Android and embedded devices. Container images based on EROFS are being used in many places these days, for example.

At the end of our February article about the debate around the composefs read-only, integrity-protected filesystem, it was predicted that the topic would come up at the 2023 Linux Storage, Filesystem, Memory-Management and BPF Summit. That happened on the second day of the summit when Alexander Larsson led a session on composefs. While the mailing-list discussion was somewhat contentious, the session was less so, since overlayfs can be made to fit the needs of the composefs use cases. It turns out that an entirely new filesystem is not really needed.

Version 15.5 of the openSUSE Leap distribution has been released. This is not intended as a feature release, but brings updated versions of many packages. The project has also announced that there will be one more 15.x release before that series ends and users have to migrate to whatever its successor will be.

Security updates have been issued by Debian (c-ares), Fedora (curl and firefox), Oracle (cups-filters, kernel, and webkit2gtk3), Red Hat (emacs and kpatch-patch), Slackware (mozilla), SUSE (kernel and openssl-1_0_0), and Ubuntu (firefox and libreoffice).

Margaret Mitchell, a researcher focused on the intersection of machine learning and ethics, was the morning keynote speaker on the third day of PyCon 2023. She spoke about her journey into machine learning and how the Python language has been instrumental in it. It was a timely and thought-provoking talk that looked beyond the machine-learning hype to consider the bigger picture.

Security updates have been issued by Debian (linux-5.10), Red Hat (cups-filters, curl, kernel, kernel-rt, kpatch-patch, and webkit2gtk3), SUSE (apache-commons-fileupload, openstack-heat, openstack-swift, python-Werkzeug, and openstack-heat, python-Werkzeug), and Ubuntu (frr, go, libraw, libssh, nghttp2, python2.7, python3.10, python3.11, python3.5, python3.6, python3.8, and xfce4-settings).

At the 2023 Linux Storage, Filesystem, Memory-Management and BPF Summit, Luis Chamberlain led a plenary session on kernel support for block sizes larger than 4KB. There are assumptions in the current kernel that the block size used by a block-layer device is less than or equal to the system's page size—both are usually 4KB today. But there have been efforts over the years to remove that restriction; that work may be heading toward fruition, in part because of the folio efforts of late, though there are still lots of areas that need attention.

The 6.3.6, 6.1.32, 5.15.115, 5.10.182, and 5.4.245 stable kernels have been released. They contain a relatively small number of important fixes throughout the kernel tree.

Developers learning the Unix (or POSIX in general) system-call set will quickly encounter file descriptors, which are used to represent open files and more. Developers also tend to learn early on that the first three file descriptors are special, with file descriptor zero being the standard input stream, one being standard output, and two being standard error. The kernel, though, does not normally attach any specific meaning to a given descriptor number, so it was somewhat surprising when a recent BPF patch series attempted to attach a special meaning to zero when used as a file descriptor.

Security updates have been issued by Debian (chromium, cpio, mariadb-10.3, nbconvert, sofia-sip, and wireshark), Fedora (ImageMagick, mingw-python-requests, openssl, python3.6, texlive-base, and webkitgtk), Red Hat (apr-util, git, gnutls, kernel, kernel-rt, and kpatch-patch), Slackware (cups and ntp), and Ubuntu (linux-azure-fde, linux-azure-fde-5.15 and perl).

Linus has released 6.4-rc5 for testing.

Nothing particularly strange here, most notable is probably just the quick revert of the module loading trial that caused problems for people in rc4 depending on just random timing luck (or rather, lack there-of). So if you tried rc4, and some devices randomly didn't work for you, that was likely the issue.

Red Hat's Matthias Clasen has let it be known that LibreOffice will be dropped from a future Red Hat Enterprise Linux release, and the future of its support in Fedora is unclear as well.

The Red Hat Display Systems team (the team behind most of Red Hat’s desktop efforts) has maintained the LibreOffice packages in Fedora for years as part of our work to support LibreOffice for Red Hat Enterprise Linux. We are adjusting our engineering priorities for RHEL for Workstations and focusing on gaps in Wayland, building out HDR support, building out what’s needed for color-sensitive work, and a host of other refinements required by Workstation users. This is work that will improve the workstation experience for Fedora as well as RHEL users, and which, we hope, will be positively received by the entire Linux community.

The tradeoff is that we are pivoting away from work we had been doing on desktop applications and will cease shipping LibreOffice as part of RHEL starting in a future RHEL version. This also limits our ability to maintain it in future versions of Fedora.

As the 2023 Linux Storage, Filesystem, Memory-Management and BPF Summit neared its conclusion, two sessions were held in the memory-management track on process-oriented topics. Mike Rapoport ran a session on memory-management documentation (or the lack thereof), while Andrew Morton talked about the state of the subsystem's development process in general. Both sessions were relatively brief and did not foreshadow substantial changes to come.