GEFS on OpenBSD: A Early Preview

[prev in list] [next in list] [ prev in thread ] [ next in thread ] List: openbsd-tech Subject: GEFS on OpenBSD: A very early preview From: ori () eigenstate ! org Date: 2026-09-15 15:45:05 Message-ID: EBB049B251DCF60A8C9A0575F6FC7DC9 () eigenstate ! org [Download RAW message or body] Before anyone asks: I am *not* proposing to put this in tree for a while yet. What is it ---------- So, as people may have seen at EuroBSD, I've got a rough, buggy, issue-filled preview of GEFS running on OpenBSD. The port is NOT ready for production, and data loss is currently expected, especially on error. However, the port has reached the state where (with some exceptions) the remaining problems are reasonably understood, and people can poke at them. For those who haven't watched my talk, GEFS is a new, crash-safe, snapshotting, copy on write FS that I wrote for 9front, and which I am in the process of moving to OpenBSD. The file system is described in full here: https://orib.dev/gefs.pdf It's under 9,000 lines of code in kernel at the moment, though I expect it'll grow a bit over time, since there's a good deal missing. Porting ------- I'm approaching this as a proper, in-kernel file system that keeps the data structure and fiddly code fairly in sync between Plan 9 and OpenBSD, but the code itself is copied and pasted. My goal is that it will continue to rhyme, so that fixes can be shared, but the requirements of the two environments means that the code probably won't be ported, and trying to shove in some abstraction layer seems like a bad idea. Problems -------- So, IMO, the biggest of the remaining problems: Consistency Protocol: This is the big unknown for me; A write to the superblock needs to come after all writes in the snapshot, but as long as it is written after the blocks have hit disk, it's safe. There are also a couple of fixes to backport from 9Front on the write ordering. Error handling and porting brain damage: Error handling is largely commented out. I'm going to have to go through the error handling paths bit by bit and convert it with care; the approach to error handling I took on 9front is not acceptable for OpenBSD. There's a few other things, like some globals being used that would prevent more than one mount at a time. Userspace tools: At least, I assume that telling people to boot 9front in a VM to create or fsck is not a good long term solution. Snapshot management and the associated ioctls will also go here. Posix persnicketies: The system that this was ported from was not a posix system, so there are likely to be many places where we don't quite get the constraints right. Regress: There's a small test suite for Plan 9. There's none for OpenBSD. Hardlinks: Easy to implement, but needs a refcount file by file. Kqueue: Easy to implement, but needs a refcount file by file. NFS: Has some ugly hooks, not sure what would be needed to add them. Other missing pieces: Things like bootloader support, adding boot environments, quotas, and other niceties; this is well down the list. Quotas, in particular, would allow LLVM to continue in its attempt to grow to the size of the known universe without us preallocating a /usr/obj of that size. I'm sure I've forgotten some. Right now: I'm not looking to fix KNF; as things get touched, I'll start to move them over, but I would prefer to keep the code closer with the original until it's closer to ready for upstreaming. There are also a few non-fatal issues independent of 9front and OpenBSD, such as slow deletions of large files; I've got ideas to improve them. Getting it ---------- as one patch: https;//orib.dev/gefs.diff The git repo is hidden on shithub, and the server is tiny and will get overloaded if people clone fresh repos from it. Instead, get a copy of the initial repo from github, and pull only the updates. # first, get a copy of the upstream from # somewhere else git clone https://github.com/openbsd/src cd src # now, add my server, and get just the diffs git remote add gefs git://shithub.us/ori/openbsd git fetch gefs git checkout -b gefs gefs/gefs Note, I will be rebasing and force-pushing the branch occasionally in order to keep up with openbsd current; commit ids will change. [prev in list] [next in list] [ prev in thread ] [ next in thread ]