[$] Toward fast, containerized, user-space filesystems

Filesystems are complex and performance-sensitive beasts. They can also
present security concerns. Microkernel-based systems have long pushed
filesystems into separate processes in order to contain any vulnerabilities
that may be found there. Linux can do the same with the Filesystem in
Userspace (FUSE) subsystem, but using FUSE brings a significant
performance penalty. Darrick Wong is working on ways to eliminate that
penalty, and he has a massive patch
set showing how ext4 filesystems can be safely implemented in user space by
unprivileged processes with good performance. This work has the potential
to radically change how filesystems are managed on Linux systems.