Re: Layered fs, vnode locking and v_vnlock removal

[David Laight <david%l8s.co.uk@localhost>]

On Wed, Jun 02, 2010 at 12:54:53AM +0200, Adam Hamsik wrote:
> > 
> > In the long term VOP_xxxLOCK() should become part of the file systems.
> 
> AFAIK there is a consensus between yamt@, ad@ and thorpej@ that
> locking should be moved down to the filesystems.
> There was some discussion about it here some time before.

There is a lurking problem making read/write atomically update the file
offset. I suspect that is currently covered by the vnode lock.
Might only affect O_APPEND - but I've seen systems get that wrong!

Not to mention the problem of correctly setting the file position
when read/write fault on a userspace address part way through a
transfer.

        David

-- 
David Laight: david%l8s.co.uk@localhost