On Tue, Dec 11, 2018 at 11:41:55AM -0700, Jens Axboe wrote:
> On Wed, Nov 28, 2018 at 11:35 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> >
> > rcu_read_lock();
> > - table = rcu_dereference(mm->ioctx_table);
> > -
> > - if (!table || id >= table->nr)
> > - goto out;
> > -
> > - ctx = rcu_dereference(table->table[id]);
> > + ctx = xa_load(&mm->ioctx, id);
> > if (ctx && ctx->user_id == ctx_id) {
> > if (percpu_ref_tryget_live(&ctx->users))
> > ret = ctx;
> > }
>
> Question on this part - do we need that RCU read lock around this now? I
> don't think we do.
I think we need the rcu read lock here to prevent ctx from being freed
under us by free_ioctx().
