[ofa-general] Re: [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges

[Christoph Lameter]

On Thu, 28 Feb 2008, Andrea Arcangeli wrote:

> > 3. Keep the refcount elevated until pages are freed in another execution 
> > context.
> 
> Page refcount is not enough (the mmu_notifier_release will run in
> another cpu the moment after i_mmap_lock is unlocked) but mm_users may
> prevent us to change the i_mmap_lock to a mutex, but it'll slowdown
> truncate as it'll have to drop the lock and restart the radix tree
> walk every time so a change like this better fits as a separate
> CONFIG_XPMEM IMHO.

Erm. This would also be needed by RDMA etc.