linux-kernel - Re: Splicing to/from a tty

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Message-ID: <CAHk-=wjtTC_jNL+K1Ey_wY_KpTYZOR5XwhkZ+Eu7vviVi5itDQ@mail.gmail.com>
Date:   Wed, 20 Jan 2021 11:27:26 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Christoph Hellwig <hch@....de>,
        Johannes Berg <johannes@...solutions.net>,
        Oliver Giles <ohw.giles@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: Splicing to/from a tty

On Wed, Jan 20, 2021 at 11:11 AM Al Viro <viro@...iv.linux.org.uk> wrote:
>
> Why do we care about O_APPEND on anything without FMODE_PWRITE (including
> pipes), anyway?  All writes there ignore position, after all...

We shouldn't care.

Also, I think we should try to move away from FMODE_PWRITE/PREAD
entirely, and use FMODE_STREAM as the primary "this thing doesn't have
a position at all".

That's what gets rid of all the f_pos locking etc after all. The
FMODE_PWRITE/PREAD flags are I think legacy (although we do seem to
have the seq_file case that normally allows position on reads, but not
on writes, so we may need to keep all three bits).

Anyway, I think that with FMODE_STREAM, O_APPEND definitely should be a no-op.

            Linus