Re: blocking vs. non-blocking mmu notifiers

[Michal Hocko <mhocko@suse.com>]

On Wed 23-03-22 14:04:04, Jason Gunthorpe wrote:
> On Wed, Mar 23, 2022 at 05:49:43PM +0100, Michal Hocko wrote:
> > > The bug here is that prior to commit a81461b0546c ("xen/gntdev: update
> > > to new mmu_notifier semantic") wired the mn_invl_range_start() which
> > > takes a mutex to invalidate_page, which is defined to run in an atomic
> > > context.
> > 
> > Yeah, we have already identified that but quickly realized that the
> > whole mmu notifier overhaul which this fix depends on would be no no for
> > backporting to our older code base. So we are trying to find our way
> > around that.
> 
> IMHO you don't need everything, just commit 369ea8242c0f ("mm/rmap:
> update to new mmu_notifier semantic v2") which adds the missing
> start/end outside the lock for the page callbacks.
> 
> Then you can take safely a8146 into gntdev.

Thanks Jason!

-- 
Michal Hocko
SUSE Labs