As expected, this was one of the bigger merge windows, almost certainly just because we had some pent-up development due to the previous releases being impacted by the holiday season. That said, while it's bigger than normal, it's not some kind of record-breaking thing.". In the end, 12.633 non-merge changesets were pulled into the mainline during this merge window. [Read more](https://lwn.net/Articles/1016577/) ## [$] The state of guest_memfd **Category:** Linux **Tags:** General **Published:** Fri, 04 Apr 2025 15:52:32 +0000 **TL;DR:** Here is a summary of the text in 2 sentences: In cloud computing, each guest running on a host shares some memory with the host, which can access that memory to gather private data from the guest. The "guest_memfd" subsystem helps remove the host's access to guest memory, making it more secure and private for the guest. A typical cloud-computing host will share some of its memory with each guest that it runs. The host retains its access to that memory, though, meaning that it can readily dig through that memory in search of data that the guest would prefer to keep private. The guest_memfd subsystem removes (most of) the host's access to guest memory, making the guest's data more secure. In the memory-management track of the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit, David Hildenbrand ran a discussion on the state and future of this feature. [Read more](https://lwn.net/Articles/1016133/) ## [$] The future of ZONE_DEVICE **Category:** Linux **Tags:** Linux **Published:** Fri, 04 Apr 2025 14:37:57 +0000 **TL;DR:** Here is a 2-sentence summary: Alistair Popple referred to ZONE_DEVICE as the "ugly stepchild" of the kernel's memory-management subsystem at the Linux Storage, Filesystem, Memory-Management, and BPF Summit, acknowledging its importance on current hardware. He aimed to discuss the challenges with ZONE_DEVICE and find ways to improve it, potentially making it more attractive or integrated into the main system. Alistair Popple started his session at the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit by proclaiming that ZONE_DEVICE is "
the ugly stepchild" of the kernel's memory-management subsystem. Ugly or not, the ability to manage memory that is attached to a peripheral device rather than a CPU is increasingly important on current hardware. Popple hoped to cover some of the challenges with ZONE_DEVICE and find ways to make the stepchild a bit more attractive, if not bring it into the family entirely. [Read more](https://lwn.net/Articles/1016124/) ## [$] Supporting untorn buffered writes **Category:** Linux **Tags:** General **Published:** Fri, 04 Apr 2025 13:39:56 +0000 **TL;DR:** Here is a summary of the text in 2 sentences: At last year's Linux Storage, Filesystem, Memory-Management, and BPF Summit, there was a discussion about adding atomic write support to the block layer and XFS filesystem. This year, Luis Chamberlain led a track at the summit to revisit the idea of providing atomic writes for buffered I/O, with the goal of simplifying writes in databases like PostgreSQL that currently require special handling to avoid torn writes. At last year's Linux Storage, Filesystem, Memory-Management, and BPF Summit (LSFMM+BPF), there was a discussion about atomic writes that was accompanied by patches to support the feature in the block layer, and for direct I/O on XFS. That work was merged, but another piece of that discussion concerned adding the feature for buffered I/O, in part because the PostgreSQL database currently has to jump through hoops to ensure that its writes are not "torn" (partially written) when there is an error or crash. Luis Chamberlain led a combined storage and filesystem track at this year's summit to revisit the idea of providing atomic (or untorn) writes for buffered I/O. [Read more](https://lwn.net/Articles/1016015/) ## [$] A strange BPF error message **Category:** Linux **Tags:** General **Published:** Fri, 04 Apr 2025 13:06:07 +0000 **TL;DR:** Here is a 2-sentence summary: Yonghong Song presented a talk at the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit about tracking down a strange verifier error message and proposed ways to improve Clang's user experience. He also discussed issues with optimizations that change function signatures, building on a previous session by José Marchesi.
Yonghong Song brought a story about tracking down the cause of a strange verifier error message to the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit. He then presented some possible ways to improve Clang's user experience for anyone running into the same class of error in the future. Toward the end of his allotted time, he also discussed the problems with optimizations that change the signature of functions — a problem that José Marchesi had also brought up in the previous session.
[Read more](https://lwn.net/Articles/1016105/)