The data is only needed by filesystems that 1. use buffer cache 2. utilize clustering write support.
ext2fs change to reset clusterw on truncation should be a bug fix.
Remove #define _KERNEL hacks from libprocstat
Make sys/buf.h, sys/pipe.h, sys/fs/devfs/devfs*.h headers usable in userspace, assuming that the consumer has an idea that it is for. Unhide more material from sys/mount.h and sys/ufs/ufs/inode.h, sys/ufs/ufs/ufsmount.h for consumption of userspace tools, with the same caveat.
Remove unacceptable hack from usr.sbin/makefs which relied on sys/buf.h being unusable in userspace, where it override struct buf with its own definition. Instead, provide struct m_buf and struct m_vnode and adapt code to use local variants.
This is the diff of the whole branch, individual commits can be seen at
https://kib.kiev.ua/git/gitweb.cgi?p=deviant3.git;a=shortlog;h=refs/heads/vn_clusterw