Linux 6.17 second half of the merge window

Linus released 6.17-rc1 on August 10 and with that the merge window for 6.17 is now closed. We had earlier covered the memory management and filesystems updates from the initial merge window.
Here are some of the other core subsystem updates for 6.17-rc1.

Block layer
Read‑ahead tuned for hard drives: Rotational disks that don’t report an “optimal I/O size” now get a larger, smarter default read‑ahead based on max I/O size.

For a SCSI disk, this defaults to 2560 KB, which significantly improve performance for buffered reads. Using XFS and sequentially reading randomly selected (large) files stored on a SATA HDD, the maximum throughput achieved with 8 readers reading files with 1MB buffered I/Os increases from 122 MB/s to 167 MB/s (+36%). The improvement is even larger when reading files using 128 KB buffered I/Os, with a throughput increasing from 57 MB/s to 165 MB/s (+189%).

F2FS:
- Folio conversion
- added several sysfs entries to tune GCs for ZUFS
- Conversion to new mount apis

ARM:
Host driver for GICv5, the next generation interrupt controller for arm64, including support for interrupt routing, MSIs, interrupt translation and wired interrupts

S390:
- Enable THP swapping and THP migration

MM (new):
- Optimizations for khugepaged: Improve khugepaged throughput by batching PTE operations for large folios. This gain is mainly for arm64.

Misc:
- Make kdump more reliable by providing an extra crashkernel=XX,cma option to allow crashkernel to reserve extra memory from CMA area for it’s runtime overhead.
More details can be found here.
- A new struct netmem_desc is introduced. This allows the page pool of netstack to refer to netmem_desc instead of struct page. This effort is a step towards memdesc world.

Bcachefs:
- No bcachefs pull request was merged this cycle. As some of you might know that expectations had already been tempered by a 6.16-rc4 note from Linus -

I have pulled this, but also as per that discussion, I think we’ll be parting ways in the 6.17 merge window…

In the 6.17 Bcachefs pull request thread, Kent added that he’d received an email from Linus saying “we’re now talking about git rm -rf in 6.18”. Things definitely aren’t looking good for bcachefs users, given that this isn’t the first time bcachefs users have faced a setback. Linus hasn’t responded anything on that thread yet. So we will have to wait until something is publicly announced on the future of bcachefs.

That wraps up the rest of 6.17’s merge window. As always with -rc1 now out, expect the usual shakedown and fixes over the next few weeks.