Re: [PATCH 1/6] mm: make mm->pinned_vm an atomic64 counter

Andrew Morton
2019-01-28T21:11:01Z

On Wed, 23 Jan 2019 11:33:53 -0700 Jason Gunthorpe <jgg@ziepe.ca> wrote:

> On Mon, Jan 21, 2019 at 09:42:15AM -0800, Davidlohr Bueso wrote:
> > Taking a sleeping lock to _only_ increment a variable is quite the
> > overkill, and pretty much all users do this. Furthermore, some drivers
> > (ie: infiniband and scif) that need pinned semantics can go to quite
> > some trouble to actually delay via workqueue (un)accounting for pinned
> > pages when not possible to acquire it.
> >
> > By making the counter atomic we no longer need to hold the mmap_sem
> > and can simply some code around it for pinned_vm users. The counter
> > is 64-bit such that we need not worry about overflows such as rdma
> > user input controlled from userspace.
>
> I see a number of MM people Reviewed-by this so are we good to take
> this in the RDMA tree now?

Please do.