5.16 Merge window, part 2

Linus Torvalds released 5.16-rc1 and ended the 5.16 merge window on November 14, as expected. At that point, 12,321 non-merge changesets had been pulled into the mainline; about 5,500 since our summary of the first half of the merge window was written. As is usually the case, the patch mix in the latter part of the merge window tended more toward fixes, but there were a number other changes as well.

Changes pulled in the latter part of the merge window include:

Architecture-specific

• The PowerPC architecture now sets the STRICT_KERNEL_RWX option by default. This prevents memory from being both executable and writable, increasing hardening overall.
• Memory hotplug is no longer supported on 32-bit x86 systems. This feature was marked as broken over one year ago; seemingly nobody complained.

Core kernel

• The DAMON operations schemes (DAMOS) patch set has been merged; this mechanism allows the use of DAMON to control page reclaim in user space. DAMON has also gained the ability to perform physical address-space monitoring.
• Only the SLUB slab allocator can be selected on systems configured for realtime preemption.

Filesystems and block I/O

• The fanotify mechanism has gained the ability to provide notifications when filesystem errors happen; this feature is meant for use by monitoring systems. There is some documentation in this commit, and this commit contains a sample program.
• The F2FS filesystem has two new mount options that instruct the kernel to fragment files across the storage device. Most users are unlikely to want to use this option, but it can be helpful for developers working on the performance of fragmented filesystems.

Hardware support

• Industrial I/O: Analog Devices ADXL355 and ADXL313 3-axis digital accelerometers, Maxim MAX31865 RTD temperature sensors, Senseair Sunrise 006-0-0007 and SCD4X CO2 sensors, NXP IMX8QXP analog-to-digital converters, and Analog Devices ADRF6780 microwave upconverters.
• Miscellaneous: Alibaba elastic network interfaces, ASPEED UART routing controllers, Qualcomm QCM2290 global clock controllers, Qualcomm SC7280 low power audio subsystem clock controllers, Qualcomm SC7280 camera clock controllers, MediaTek MT8195 clocks, NXP i.MX8ULP CCM clock controllers, HiSilicion hi3670 PCIe PHYs, Nintendo switch controllers, Amlogic Meson6/8/8b/8m2 AO ARC remote processors, NXP i.MX DSP remote processors, MStar MSC313 realtime clocks, Cypress StreetFighter touchkey controllers, and Sharp LS060T1SX01 FullHD video mode panels.
• PCI: MediaTek MT7621 PCIe host controllers and Qualcomm PCIe endpoint controllers.
• Pin control: Qualcomm SM6350 and QCM2290 pin controllers, UniPhier NX1 SoC pin controllers, ZynqMP ps-mode pin GPIO controllers, Mediatek MT7986 pin controllers, and Apple SoC GPIO pin controllers.
• Sound: Realtek ALC5682I-VS codecs, NVIDIA Tegra 210 AHUB audio hubs, Nuvoton NAU88L21 audio codecs, Rockchip I2S/TDM audio controllers, Richtek RT9120 Stereo class-D amplifiers, Qualcomm asynchronous general packet router buses, Qualcomm Audio Process Manager digital audio interfaces, and Maxim integrated MAX98520 speaker amplifiers.

Miscellaneous

• The zstd compression code bundled into the kernel has been updated to version 1.4.10 — the first update in four years. There have been a lot of changes, including the addition of a new, more kernel-like wrapper API. See this merge commit for more information.

Security-related

• The device-mapper subsystem is now able to generate audit events.
• The final change pulled before the 5.16-rc1 release completed the task of eliminating implicit fall-throughs in switch statements. Specifically, the -Wimplicit-fallthrough warning has been enabled to flag any attempts to add any new uses of that pattern.

Internal kernel changes

• The exported symbols for the DMA-BUF API have been moved into a separate namespace as an indication that they are not intended for general use. This was one of the outcomes of this Maintainers Summit session on accelerator drivers. The Habana accelerator driver work that provoked much of this discussion has also been merged.
• The patch set replacing congestion_wait() has been merged. Using congestion to regulate memory reclaim has not worked for years; the relevant code has finally been fixed.
• The liblockdep library has been removed from the kernel tree in favor of maintaining it externally going forward.

If the usual nine-week schedule is followed, the 5.16 release can be expected to happen on January 2. Given the presence of the holidays just before that date, it would not be entirely surprising to see the schedule slip by a week. Either way, there is a lot of testing and fixing to be done between now and then.

Index entries for this article
Kernel	Releases/5.16

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