4.18 Merge window, part 2
By the time that Linus Torvalds released 4.18-rc1 and closed the merge
window for this development cycle, 11,594 non-merge changesets had
found their way into the mainline kernel repository. Nearly 4,500 of those
were pulled after last week's summary was
written. Thus, in terms of commit traffic, 4.18 looks to be quite similar
to its predecessors. As usual, the entry of significant new features has
slowed toward the end of the merge window, but there are still some
important changes on the list.
Core kernel
- Asynchronous I/O operations can be submitted with the new IOCB_FLAG_IOPRIO flag to set the I/O priority of individual operations.
- After years of discussion, restartable sequences have finally made it into the mainline kernel, with support on the x86, ARM, and PowerPC architectures. The associated "ops vector" functionality was not merged, and doesn't appear likely to go in anytime soon.
Architecture-specific
- The ARM64 architecture has gained mitigations for the Spectre version 4 vulnerability.
- The IA64 "perfmon" performance-monitoring feature has been marked broken, due to a set of internal problems that have been discovered. Before fixing those problems, the developers want to see if anybody even notices the removal of perfmon; there is a strong suspicion that nobody is actually using it.
- Among the many new systems-on-chip supported in this release, there is
incomplete support for the Qualcomm Snapdragon 845, found in high-end
mobile devices. Olof Johansson wrote: "
It's great to see mainline support for it. So far, you can't do much with it, since a lot of peripherals are not yet in the DTs but driver support for USB, GPU and other pieces are starting to trickle in. This might end up being a well-supported SoC upstream if the momentum keeps up
".
Filesystems and block layer
- As was covered recently, support for the Lustre filesystem has been removed from the staging tree.
- The F2FS filesystem has improved discard support, addressing some responsiveness problems experienced in the past.
- The new "writecache" device-mapper target can be used to cache block writes to a persistent-memory or solid-state device. See Documentation/device-mapper/writecache.txt for more information.
Hardware support
- Valve Steam game controllers, Silergy SY8106A regulators, ROHM BD71837 power regulators, Freescale DPAA2 1588 timer modules, Texas Instruments DAC5571 digital-to-analog converters, Qualcomm MSM8998 and SDM845 global clock controllers, Qualcomm SDM845 video clock controllers, Zorro ESP SCSI adapters, RAVE SP backlight controllers, and ORISE Technology OTM3225A backlight controllers.
Internal kernel changes
- There has been an extensive set of changes to make the kernel use
overflow-safe allocation calls whenever possible. Thus, for example,
calls that looked like:
kmalloc(count*size, gfp_flags);have been changed to:
kmalloc_array(count, size, gfp_flags); - The configuration options for stack protection have been changed. This is a result of the new configuration language work, which makes it possible to select the strongest available stack protection automatically, but which could have the opposite effect in some existing configurations. See this commit for details.
The net result of all the changes in 4.18 looks to be a net reduction of nearly 100,000 lines of code. That is only the fourth time in kernel development history that a release has been smaller than its predecessor, and the only time that this has happened for two releases in a row.
The stabilization period for 4.18 has now begun, with the final release
expected on August 5 or 12.
| Index entries for this article | |
|---|---|
| Kernel | Releases/4.18 |