Matthew Wilcox from Oracle, known for creating the nvme (NVM Express) driver and the DAX filesystem direct access mechanism, proposed removing the ReiserFS filesystem from the Linux kernel, similar to the previously removed legacy filesystems ext and xiafs, or to reduce the ReiserFS code, keeping only read-only mode support.
The motive for removal stems from the additional difficulties in modernizing the kernel infrastructure caused by the necessity to retain the outdated AOP_FLAG_CONT_EXPAND flag handler in the kernel specifically for ReiserFS, as it remains the only filesystem utilizing this flag in the write_begin function. The last code update for ReiserFS dates back to 2019, and it is unclear how much this filesystem is still in demand and whether it continues to be used.
Jan Kára from SUSE agreed that ReiserFS is on the path to obsolescence, but it remains uncertain whether it has aged sufficiently to warrant removal from the kernel. According to Jan, ReiserFS continues to be shipped with openSUSE and SLES, but the user base for this filesystem is negligible and continually decreasing. Support for ReiserFS for enterprise users at SUSE was discontinued 3-4 years ago, and the ReiserFS module is not included by default in the kernel package. As a suggestion, Jan proposed to start issuing deprecation warnings when mounting ReiserFS partitions and to consider this filesystem ready for removal if no one expresses a desire to continue using it within a year or two.
The discussion was joined by Eduard Shishkin, the maintainer of the ReiserFS filesystem, who provided a patch removing the use of the AOP_FLAG_CONT_EXPAND flag from the ReiserFS code. Matthew Wilcox accepted the patch into his branch. Thus, the reason for removal has been eliminated, and the question of excluding ReiserFS from the kernel can be considered deferred for a considerable time.
It is impossible to completely disregard the issue of ReiserFS obsolescence due to work aimed at removing file systems with unresolved 2038 problems from the kernel. For example, for this reason, a schedule has already been prepared for the removal of version four of the XFS file system from the kernel (the new XFS format was proposed in kernel 5.10 and pushed the time counter overflow to the year 2468). The XFS v4 build will be disabled by default in 2025, and the code will be removed in 2030. A similar schedule is proposed to be developed for ReiserFS, allowing at least five years for migration to other file systems or an altered metadata format.
Source: opennet.ru
