EROFS (Enhanced Read-Only File System) is a lightweight read-only
file system with modern designs (e.g. no buffer heads, inline
xattrs/data, chunk-based deduplication, multiple devices, etc.) for
scenarios which need high-performance read-only solutions, e.g.
smartphones with Android OS, LiveCDs and high-density hosts with
numerous containers;

It also provides fixed-sized output compression support in order to
improve storage density as well as keep relatively higher compression
ratios and implements in-place decompression to reuse the file page
for compressed data temporarily with proper strategies, which is
quite useful to ensure guaranteed end-to-end runtime decompression
performance under extremely memory pressure without extra cost.

See the documentation at Documentation/filesystems/erofs.rst
for more details.

If unsure, say N.

source code:

fs/erofs/