The main feature being added to EROFS with Linux 5.13 is "big pcluster" support, which will allow EROFS to compress data into more than one file-system block. Basically, EROFS big pcluster allows for compressing variable-sized input to variable-sized blocks. Performance figures and more technical details on the implementation can be found via this patch series .
In addition to the big pcluster support there is also support for on-disk compression configurations and initially is being used for storing on-disk LZ4 compression configurations. EROFS in Linux 5.13 is also seeing other data compression handling improvements and a variety of fixes and code clean-ups.
More details on these enhanced read-only file-system improvements for Linux 5.13 via this pull request .