EXT4 Introducing IOmap Buffered I/O Path With Some Performance Gains

EXT4 with the upcoming Linux 7.4 kernel looks like it will introduce opt-in support for IOmap buffered I/O in replacing the file-system's buffer_head usage with IOmap. IOmap is the modern Linux framework for mapping file offsets to device blocks compared to the older buffer_head approach. The IOmap usage is more efficient and better integrated with Linux's folios while also not having some of the high memory overhead of buffer heads. Zhang Yi of Huawei has been working to convert the EXT4 buffered I/O path over to using IOmap. The switch-over has shown some impressive performance benefits while also some regressions. The v6 cover letter has many benchmarks in different configurations for EXT4 with IOmap over the current baseline of using buffer heads. Due to the IOmap buffered I/O code path not implementing all existing EXT4 features yet, it's not enabled by default. The code adds a "buffered_iomap" mount option if wanting to use EXT4 with the new IOmap code path. Ted Ts'o this past week queued all of those IOmap buffered I/O patches into EXT4's dev branch. With those patches now in the EXT4 dev branch, it looks like they will be submitted for the upcoming Linux 7.4 merge window.