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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sun, 24 Jan 2021 11:11:42 -0800
Message-ID: <CAHk-=wgrkX4KM-kbEzs+Bap4v13RQ-ymwwAxgwjhTz6VVtp8Cw@mail.gmail.com>
Subject: Re: Splicing to/from a tty
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Johannes Berg <johannes@sipsolutions.net>,
        Christoph Hellwig <hch@lst.de>,
        Oliver Giles <ohw.giles@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Al,
 coming back to this because rc5 is imminent..

On Mon, Jan 18, 2021 at 11:45 AM Al Viro <viro@zeniv-ca> wrote:
>
> do_splice_direct() does something that do_splice() won't - it
> handles non-pipe to non-pipe case.  Which is how sendfile(2) is
> normally used, of course.
>
> I'll look into that in more details, but IMO bothering with
> internal pipe is just plain wrong for those cases.

You clearly thought about this, with the emails about odd error cases,
but I get the feeling that for fixing the current "you can't
sendfile() to a pipe" regression (including stable) we should do the
one-liner. No?

I agree that it would be better fixed by just having sendfile()
basically turn into splice() for the pipe target case, but I haven't
seen any patches from you, so I assume it wasn't 100% trivial.

Hmm?

              Linus