ReiserFS is a journaling filesystem, i.e., the system that uses the journal data structure to record the changes not yet committed to the central part of the filesystem. ReiserFS was the first system of this kind that was integrated into the standard Linux kernel. It supports fast tree rebuilding, a wide array of recovery capabilities, and tail packing for reducing internal fragmentation.
Due to a lack of upstream updates, ReiserFS was deprecated in Linux 5.18 and marked obsolete in kernel version 6.6.
