I have limited Linux (a few janitorial patches and attempts to fix some kernel.org bugs) or ext4 development experience, but am looking to help out. I completed the eudyptula challenges and am pretty familiar with git, configuring/building a kernel, building a specific module, testing in a VM, checkpatch.pl, git-send-email, etc.
Broader experience: More recently, slightly less limited FreeBSD kernel and filesystem development; although mostly for a derived proprietary OS for work, and less upstream contribution (c'est la FreeBSD).
Further back, I've been a Linux user since ~2004, Fedora contributor since ~2007, some history of open-source userspace projects on Sourceforge, Github. Made some attempt to port FUSE (API-compatable for Unix FUSE filesystems) to Windows NT in University (not especially successfully, but ...). Mucked about with VFAT for a different university project (directories with sorted dirents on directory modification).