Linux 5.15 Delivers Many Features With New NTFS Driver, In-Kernel SMB3 Server, New Hardware

Written by Michael Larabel in Software on 13 September 2021 at 09:16 AM EDT.

Feature development is over on the Linux 5.15 kernel with Linux 5.15-rc1 being issued. It's now on to testing and bug fixing over the next two months before the kernel is christened as stable. Here is our original Linux 5.15 feature overview about all of the big changes in this next kernel version.

With Linux 5.15 there is continued bring-up for Intel Alder Lake, a lot of AMD changes compared to usual, the Apple M1 IOMMU driver that is an important step for enabling more Apple Silicon / M1 SoC functionality under Linux, the shiny new NTFS file-system driver, KSMBD as an in-kernel high performance SMB3 file server, support for yet-to-be-released Intel "Bz" WiFi hardware, initial support for Intel DG2/Alchemist graphics along with XeHP, a bulk of the real-time (RT) kernel support is in place with the PREEMPT_RT locking code merged, and the controversial opt-in L1 data cache flushing code also made it into Linux 5.15.

Here is a more detailed look at all of the Linux 5.15 changes coming for this next stable kernel. As 2021 is drawing near, it's also possible Linux 5.15 could serve as this year's LTS kernel version... We'll see.


- The AMD PDTDMA driver was merged after being in development for two years to benefit AMD EPYC server processors.

- Expanded stack randomization for RISC-V along with other features wired up for RISC-V.

- Alder Lake support in the TCC driver.

- An important AMD laptop suspend/resume fix benefiting various models.

- KVM now defaults to the new x86 TDP MMU and adds AMD SVM 5-level paging.

- AMD Zen 3 APU temperature monitoring is finally in place.

- Yellow Carp APU temperature monitoring support.

- The AMD SB-RMI driver was merged for benefiting servers with use-cases such as the Linux-based OpenBMC software stack.

- Optimized C3 entry handling for AMD CPUs albeit long overdue.

- Some IRQ kernel code improvements to benefit Intel 486 era hardware.

- An AVX2-optimized SM4 cipher implementation.


- Many new RDNA2 PCI IDs pointing to a possible RDNA2 graphics card refresh.

- AMD Cyan Skillfish graphics support.

- Initial support for Intel XeHP and DG2/Alchemist discrete graphics.

- Removal of Intel Gen10 / Cannon Lake graphics support.

- Many other graphics improvements among the DRM/KMS drivers.

Storage / File-Systems:

- The new NTFS driver was merged, a big improvement over the existing NTFS driver. This new driver is the "NTFS3" driver created by Paragon Software.

- Samsung's KSMBD was merged as an in-kernel SMB3 file server.

- OverlayFS has better performance and copying up more attributes.

- FUSE now allows mounting an active device.

- Performance optimizations for F2FS.

- Connection sharing across multiple NICs with the NFS client code.

- New optimizations for EXT4.

- A lot of improvements for XFS.

- Degraded RAID mode support for Btrfs and performance improvements.

- Btrfs support for IDMAPPED mounts and Btrfs FS-VERITY support.

- Linux 5.15 I/O can achieve up to ~3.5M IOPS per-core.

- Support for a global county / disk sequence number for disk events, requested by systemd developers.

- Removal of the LightNVM subsystem.

- Fixing up Linux's floppy disk driver code.

- Other block subsystem changes.

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