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The introduction of an explicit cache_size configuration allows customization of the cache buffers independently from the hardware read/write sizes. This has been one of littlefs's main handicaps. Without a distinction between cache units and hardware limitations, littlefs isn't able to read or program _less_ than the cache size. This leads to the counter-intuitive case where larger cache sizes can actually be harmful, since larger read/prog sizes require sending more data over the bus if we're only accessing a small set of data (for example the CTZ skip-list traversal). This is compounded with metadata logging, since a large program size limits the number of commits we can write out in a single metadata block. It really doesn't make sense to link program size + cache size here. With a separate cache_size configuration, we can be much smarter about what we actually read/write from disk. This also simplifies cache handling a bit. Before there were two possible cache sizes, but these were rarely used. Note that the cache_size is NOT written to the superblock and can be freely changed without breaking backwards compatibility.