Re: Btrfs for mainline

Matthew Wilcox
2009-01-03T19:17:24Z

On Fri, Jan 02, 2009 at 08:05:50PM +0100, Andi Kleen wrote:
> Some items I remember from my last look at the code that should
> be cleaned up before mainline merge (that wasn't a full in depth review):
>
> - locking.c needs a lot of cleanup.
> If combination spinlocks/mutexes are really a win they should be
> in the generic mutex framework. And I'm still dubious on the hardcoded
> numbers.

I don't think this needs to be cleaned up before merge. I've spent
an hour or two looking at it, and while we can do a somewhat better
job as part of the generic mutex framework, it's quite tricky (due to
the different <asm/mutex.h> implementations). It has the potential to
introduce some hard-to-hit bugs in the generic mutexes, and there's some
API discussions to have.

It's no worse than XFS (which still has its own implementation of
'synchronisation variables', a (very thin) wrapper around mutexes, a
(thin) wrapper around rwsems, and wrappers around kmalloc and kmem_cache.

> - compat.h needs to go

Later. It's still there for XFS.

> - there's various copy'n'pasted code from the VFS (like may_create)
> that needs to be cleaned up.

No urgency here.

> - there should be manpages for all the ioctls and other interfaces.

I wonder if Michael Kerrisk has time to help with that. Cc'd.

> - ioctl.c was not explicitely root protected. security issues?

This does need auditing.

> - some code was severly undercommented.
> e.g. each file should at least have a one liner
> describing what it does (ideally at least a paragraph). Bad examples
> are export.c or free-space-cache.c, but also others.

Nice to have, but generally not required.

> - ENOMEM checks are still missing all over (e.g. with most of the
> btrfs_alloc_path callers). If you keep it that way you would need
> at least XFS style "loop for ever" alloc wrappers, but better just
> fix all the callers. Also there used to be a lot of BUG_ON()s on
> memory allocation failure even.
> - In general BUG_ONs need review I think. Lots of externally triggerable
> ones.

Agreed on these two.

> - various checkpath.pl level problems I think (e.g. printk levels)

Can be fixed up later.

> - the printks should all include which file system they refer to

Ditto.

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."