On Wed, Jun 02, 2010 at 05:58:40PM +0100, David Laight 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.
Yes, this keeps coming up and I keep trying to explain why it's misguided. > 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. Other important cases include atomicity of O_CREAT and permission checks done in VFS-level code. These cases can all be "handled" by cutting and pasting the code into every file system, but we really don't want to do that. -- David A. Holland dholl...@netbsd.org