linux-kernel - [PATCH v2 08/11] tty: splice

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Message-ID: <4dec932dcd027aa5836d70a6d6bedd55914c84c2.1703126594.git.nabijaczleweli@nabijaczleweli.xyz>
Date: Thu, 21 Dec 2023 04:09:10 +0100
From: 
	Ahelenia Ziemiańska <nabijaczleweli@...ijaczleweli.xyz>
Cc: Jens Axboe <axboe@...nel.dk>, Christian Brauner <brauner@...nel.org>, 
	Alexander Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-serial@...r.kernel.org
Subject: [PATCH v2 08/11] tty: splice_read: disable

We request non-blocking I/O in the generic copy_splice_read, but
"the tty layer doesn't actually honor the IOCB_NOWAIT flag for
various historical reasons.". This means that a tty->pipe splice
will happily sleep with the pipe locked forever, and any process
trying to take it (due to an open/read/write/&c.) will enter
uninterruptible sleep.

This also masks inconsistent wake-ups (usually every second line)
when splicing from ttys in icanon mode.

Link: https://lore.kernel.org/linux-fsdevel/CAHk-=wimmqG_wvSRtMiKPeGGDL816n65u=Mq2+H3-=uM2U6FmA@mail.gmail.com/
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@...ijaczleweli.xyz>
---
 drivers/tty/tty_io.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 06414e43e0b5..50c2957a9c7f 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -465,7 +465,6 @@ static const struct file_operations tty_fops = {
 	.llseek		= no_llseek,
 	.read_iter	= tty_read,
 	.write_iter	= tty_write,
-	.splice_read	= copy_splice_read,
 	.splice_write	= iter_file_splice_write,
 	.poll		= tty_poll,
 	.unlocked_ioctl	= tty_ioctl,
@@ -480,7 +479,6 @@ static const struct file_operations console_fops = {
 	.llseek		= no_llseek,
 	.read_iter	= tty_read,
 	.write_iter	= redirected_tty_write,
-	.splice_read	= copy_splice_read,
 	.splice_write	= iter_file_splice_write,
 	.poll		= tty_poll,
 	.unlocked_ioctl	= tty_ioctl,
-- 
2.39.2

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