Re: RFC: hold i_rwsem until aio completes

[Christoph Hellwig]

On Wed, Jan 15, 2020 at 02:03:22PM -0500, Waiman Long wrote:
> >> (1) no unlocking by another process than the one that acquired it
> >> (2) no return to userspace with locks held
> > As an example flow: obtain the read side lock, schedual a work queue,
> > return to user space, and unlock the read side from the work queue.
> 
> We currently have down_read_non_owner() and up_read_non_owner() that
> perform the lock and unlock without lockdep tracking. Of course, that is
> a hack and their use must be carefully scrutinized to make sure that
> there is no deadlock or other potentially locking issues.

That doesn't help with returning to userspace while the lock is held.