Re: iov_iter_pipe warning.

[Christoph Hellwig]

On Mon, Sep 11, 2017 at 12:07:23AM +0100, Al Viro wrote:
> BTW, another problem I see there is that iomap_dio_actor() should *NOT*
> assume that do-while loop in there will always manage to shove 'length'
> bytes out in case of success.  That is simply not true for pipe-backed
> destination.  And I'm not sure if outright failures halfway through
> are handled correctly.  What does it need a copy of dio->submit.iter for,
> anyway?  Why not work with dio->submit.iter directly?
> --

So that we only walk the pagetables and pin down the pages that
we can actually use in this iteration.