[$] Improving pseudo filesystems

The eventfs filesystem provides an interface to the tracepoints that are availableto be used by various Linux tracing tools (e.g. ftrace, perf, uprobes,etc.); it is meant to be a version of the tracefs filesystem thatdynamically allocates its entries as needed. The goal is to reduce the memoryrequired for multiple instances of tracefs, as Steven Rostedt described ina session at the 2022Linux Storage,Filesystem, Memory Management, and BPF Summit. He returned to the 2024edition of the summit to talk further about how to make pseudo (or virtual)filesystems, such as tracefs/eventfs, more like regular Linux filesystems,where the directory entries (dentries) and inodes are only created (andcached) as needed.