linux-kernel - Re: 4.9.0 regression in pipe-backed iov

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Message-ID: <CA+55aFyy8psMaO-wfKFBLy-icAxZyQ8DZqO5kwsPnWHPe_Z6xw@mail.gmail.com>
Date:   Thu, 12 Jan 2017 15:14:41 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     "Alan J. Wylie" <alan@...ie.me.uk>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: 4.9.0 regression in pipe-backed iov_iter with systemd-nspawn

On Thu, Jan 12, 2017 at 3:02 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Looking at the callers of "do_splice_to()", we already have the
> wait_for_space() in do_splice(), but we do *not* have it in the
> do_splice_from() case when both the input and output file descriptors
> are pipes.

Bah. That case doesn't even trigger the new code. I was lazy with my
grep. The two cases are "do_splice()" (which does have the
wait-for-space) and splice_direct_to_actor(). And
splice_direct_to_actor() shouldn't even need it, should it?

So ignore that. But I think there is something about the EAGAIN.

                  Linus