Re: 4.9.0 regression in pipe-backed iov_iter with systemd-nspawn

[Al Viro]

On Fri, Jan 13, 2017 at 12:32:37PM -0800, Linus Torvalds wrote:

> Ugh. I still think your patch is butt-ugly, and the index comparisons
> make me nervous, but..

No arguments here - 6am on 20-odd hours of uptime is _not_ a good time
for writing, especially since the data structure needs better documentation
and probably a couple of inlined helpers.  I'll try to massage the damn
thing into more readable form.

> Let's see if Alan's issue actually goes away with your later patch.

*nod*

I'm fairly sure this is the root cause of what's going on there, but it would
be nice to have an experimental confirmation.