Why zlib for UBIFS? Why not zstd?

Trying to slim down a kernel to fit the kernel partition, I built a kernel without zlib. I was surprised to see OpenWrt failing to mount overlay ubi volume because of missing zlib compressor for ubifs.

  1. Why is OpenWrt still using zlib and not zstd?
  2. I would like to build my OpenWrt image with zstd instead. Where / how do I change the compressor?


I found this commit: https://github.com/openwrt/openwrt/commit/c4d39c4d5f66d5c96131737f7905c96c258d82ba
Apparently zstd should already be the default compressor, yet somehow on my system I got zlib instead.

OpenWrt git master from last week, mvebu / Linksys WRT1900ACSv1 (shelby), kernel v5.15.