[v2] Remaining BKL users, what to do

This is a update on the current progress for the BKL removal, reflecting
what is currently in linux-next.

Maybe we can briefly discuss this at the kernel summit to decide if we
want a quick death of the BKL, i.e. fixing/disabling/staging-out the
remaining users in 2.6.38 or rather leave them there indefinitely.

On Thursday 16 September 2010, Arnd Bergmann wrote:

The big kernel lock is gone from almost all code in linux-next, this is
the status of what I think will happen to the remaining users:

drivers/gpu/drm/i810/{i810,i830}_dma.c:
	Fixable, but needs someone with the hardware to test. Can probably be
	marked CONFIG_BROKEN_ON_SMP if nobody cares.

Still open, no good solution for this.

drivers/media/video (V4L):
	Mauro is working on it, some drivers get moved to staging while the
	others get fixed. An easy workaround would be possible by adding
	per-driver mutexes, but Mauro wants to it properly by locking all
	the right places.

Progressing well, patches are being worked on.

fs/adfs:
	Probably not hard to fix, but needs someone to test it.
	adfs has only seen janitorial fixes for the last 5 years.
	Do we know of any users?

Nobody replied.

fs/autofs:
	Pretty much dead, replaced by autofs4. I'd suggest moving this
	to drivers/staging in 2.6.37 and letting it die there.

Now in staging.

fs/coda:
	Coda seems to have an active community, but not all of their
	code is actually part of linux (pioctl!), while the last official
	release is missing many of the cleanups that were don in Linux.
	Not sure what to do, if someone is interested, the best way might
	be a fresh start with a merger of the mainline linux and the
	coda.cs.cmu.edu	codebase in drivers/staging.
	Just removing the BKL without the Coda community seems like a heap
	of pointless work.

Jan Harkes showed interest, looks like this will get fixed eventually,
but probably not in time for 2.6.37.

fs/freevxfs:
	Uses the BKL in readdir and lookup, should be easy to fix. Christoph?

Still waiting for confirmation from Christoph Hellwig that the BKL
is not needed here. I can do the patch to remove it then.

fs/hpfs:
	Looks fixable, if anyone cares. Maybe it's time for retirement in
	drivers/staging though. The web page only has a Link to the
	linux-2.2 version.

No replies.

fs/lockd:
	Trond writes that he has someone working on BKL removal here.

Bryan Schumaker took care of this, looks like the locking is independent
of the fs/locks.c locking now, although it still uses the BKL internally.

I assume that this will get fixed as well, doesn't seem hard. As long
as lockd uses the BKL, both nfs and nfsd depend on the BKL implicitly.

fs/locks.c:
	Patch is under discussion, blocked by work on fs/lockd currently.

No longer blocked now, both lockd and ceph can deal with this converted
to spinlocks. I will follow up with the final patch once they hit mainline.

fs/ncpfs:
	Should be fixable if Petr still cares about it. Otherwise suggest
	moving to drivers/staging if there are no users left.

Fixed by Petr Vandrovec.

fs/qnx4:
	Should be easy to fix, there are only a few places in the code that
	use the BKL. Anders?

Anders Larsen volunteered.

fs/smbfs:
	Last I heard this was considered obsolete. Should be move it to
	drivers/staging now?

Now in staging.

fs/udf:
	Not completely trivial, but probably necessary to fix. Project web
	site is dead, I hope that Jan Kara can be motivated to fix it though.

Jan Kara volunteered to do it.

fs/ufs:
	Evgeniy Dushistov is maintaining this, I hope he can take care of
	getting rid of the BKL in UFS.

No replies.

kernel/trace/blktrace.c:
	Should be easy. Ingo? Steven?

Done.

net/appletalk:
net/ipx/af_ipx.c:
net/irda/af_irda.c:
	Can probably be saved from retirement in drivers/staging if the
	maintainers still care.

Samuel Ortiz fixed irda.

David Miller volunteered to do appletalk and ipx.

net/x25:
	Andrew Hendry has started working on it.

Patches have shown up in -next now, I suppose Andrew will finish it soon.

Out of the remaining modules, I guess i810/i830, adfs, hpfs and ufs might end
up not getting fixed at all, we can either mark them non-SMP or move them
to drivers/staging once all the others are done.

	Arnd