Usually I do not cover Linux kernels releases here, but version 5.2 is something special. Besides various performance improvements, new drivers and APIs, it is the first version of the kernel to feature a case insensitive Ext4 file system option.
The key changes in the release are as follows:
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- Sound Open Firmware for DSP audio devices
- New mount API for mounting file systems: fsopen(), open_tree(), fspick(), fsmount(), fsconfig() and move_mount().
- New open source drivers for Mali GPU on ARM
- Performance improvements made to the BFQ I/O scheduler.
- A new kernel module dm-dust that allows simulation bad blocks on drives.
Security and reliabilty
The kernel supports a new boot parameter mitigations= that allows configuring and disabling various vulnerability protections in [mostly] Intel CPUs.
-
mitigations=off- disables everything. - mitigations=auto - enables all applicable mitigation options automatically but keeps Hyper-Threading on.
- mitigations=auto,nosmt - same as above + disables Hyper Threading.
Kernel 5.2 including extra protection against Microarchitectural Data Sampling, MDS for Intel CPUs. You can check its state under
/sys/devices/system/cpu/vulnerabilities/mds
There are two modes supported, the first one relies on the updated CPU microcode, another one is a code hack. It has its own boot parameter, mds= which can be set to
mds=full-
mds=full,nosmt<-- this disables Hyper Threading mds=off
Drivers
The new kernel includes a number of new drivers, including Lima for GPU Mali 400/450, and Panfrost for Mali Midgard (Mali-T6xx, Mali-T7xx, Mali-T8xx) and Bifrost (Mali G3x, G5x, G7x).
The i915 Intel driver now supports Elkhartlake (Gen11) chips.
The amdgpu driver for GPU AMD Vega20 now supports RAS. Also, the driver has received plenty of other improvements, including the SMU 11 power management technology.
Case insensitive ext4 file system option
A new attribute, +F (EXT4_CASEFOLD_FL), can be set for a directory. When the attribute is set, all file name comparison operations will ignore the letter case. File names like Test.txt, test.txt and test.TXT will be treated as the same file name. The attribute +F is stored inside the inode area and is applicable to all files and subdirectories.
The attribute is not enabled by default. Out of the box, ext4 remains case-sensitive.
The patches were created by Canonical's developer, Gabriel Krisman Bertazi, and accepted to the mainstream after seven tries.
You can get the kernel source code here.
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Is there any article that will mention HOW to enable casefold? It’s driving me crazy that all google results only show me all this identical articles mentioning that it is now possible and nowhere can I find how to enable it. You have to enable it with tune2fs BEFORE you can use chattr, so mentioning chattr and not tune2fs is totally useless.