From Kent Overstreet <> Subject bcachefs status update (it's done cooking; let's get this sucker merged) Date Mon, 10 Jun 2019 15:14:08 -0400 Last status update: https://lkml.org/lkml/2018/12/2/46



Current status - I'm pretty much running out of things to polish and excuses to

keep tinkering. The core featureset is _done_ and the list of known outstanding

bugs is getting to be short and unexciting. The next big things on my todo list

are finishing erasure coding and reflink, but there's no reason for merging to

wait on those.



So. Here's my bcachefs-for-review branch - this has the minimal set of patches

outside of fs/bcachefs/. My master branch has some performance optimizations for

the core buffered IO paths, but those are fairly tricky and invasive so I want

to hold off on those for now - this branch is intended to be more or less

suitable for merging as is.



https://evilpiepirate.org/git/bcachefs.git/log/?h=bcachefs-for-review



The list of non bcachefs patches is:



closures: fix a race on wakeup from closure_sync

closures: closure_wait_event()

bcache: move closures to lib/

bcache: optimize continue_at_nobarrier()

block: Add some exports for bcachefs

Propagate gfp_t when allocating pte entries from __vmalloc

fs: factor out d_mark_tmpfile()

fs: insert_inode_locked2()

mm: export find_get_pages()

mm: pagecache add lock

locking: SIX locks (shared/intent/exclusive)

Compiler Attributes: add __flatten



Most of the patches are pretty small, of the ones that aren't:



- SIX locks have already been discussed, and seem to be pretty uncontroversial.



- pagecache add lock: it's kind of ugly, but necessary to rigorously prevent

page cache inconsistencies with dio and other operations, in particular

racing vs. page faults - honestly, it's criminal that we still don't have a

mechanism in the kernel to address this, other filesystems are susceptible to

these kinds of bugs too.



My patch is intentionally ugly in the hopes that someone else will come up

with a magical elegant solution, but in the meantime it's an "it's ugly but

it works" sort of thing, and I suspect in real world scenarios it's going to

beat any kind of range locking performance wise, which is the only

alternative I've heard discussed.



- Propaget gfp_t from __vmalloc() - bcachefs needs __vmalloc() to respect

GFP_NOFS, that's all that is.



- and, moving closures out of drivers/md/bcache to lib/.



The rest of the tree is 62k lines of code in fs/bcachefs. So, I obviously won't

be mailing out all of that as patches, but if any code reviewers have

suggestions on what would make that go easier go ahead and speak up. The last

time I was mailing things out for review the main thing that came up was ioctls,

but the ioctl interface hasn't really changed since then. I'm pretty confident

in the on disk format stuff, which was the other thing that was mentioned.



----------



This has been a monumental effort over a lot of years, and I'm _really_ happy

with how it's turned out. I'm excited to finally unleash this upon the world.



