Re: [PATCH] aio: Convert ioctx_table to XArray

[Jens Axboe <axboe@kernel.dk>]

On Wed, Nov 28, 2018 at 11:35 AM Matthew Wilcox <willy@infradead.org> wrote:
> @@ -1026,24 +979,17 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id)
>         struct aio_ring __user *ring  = (void __user *)ctx_id;
>         struct mm_struct *mm = current->mm;
>         struct kioctx *ctx, *ret = NULL;
> -       struct kioctx_table *table;
>         unsigned id;
>
>         if (get_user(id, &ring->id))
>                 return NULL;
>
>         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.

-- 
Jens Axboe