The EXT4 changes landed for the Linux 7.4 merge window, and the headline is opt-in buffered iomap support. It swaps the old buffer-head path for the kernel’s iomap framework, and Ted Ts’o says “large writes show significant performance improvements.” Zhang Yi of Huawei led the work.
The catch
It’s off by default. You turn it on with the buffered_iomap mount option, and it doesn’t support online defrag, inline data, fsverity, fscrypt, non-extent inodes or data=journal. If something needs one of those, ext4 falls back to the old I/O path automatically. Reads get a more modest bump than writes.
The same pull also brings fast-commit fixes and fixes for deadlocks and out-of-bounds reads on corrupted file systems.
My take
Free speed on the file system most of us already run is a nice gift. Once 7.4 ships, I’ll try it on a scratch disk before it goes anywhere near a box I care about, and so should you. If you use fscrypt, it’s not for you yet.
God Bless, and Use the Source!
