From b87e3c9610e3ffb3a46db764578b71a8b991ec19 Mon Sep 17 00:00:00 2001
From: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Date: Thu, 10 Aug 2023 11:14:55 +0200
Subject: [PATCH] tty: don't pass write() to do_tty_write()

References: bsc#1214683 (PREEMPT_RT prerequisite backports)
Patch-mainline: v6.6-rc1
Git-commit: f47a4fd67f2a803f205db7a4136571c2bd487297

write() passed to do_tty_write() is always ld->ops->write(). Instead,
align with iterate_tty_read() and pass the whole ld instead. This makes
the code easier to follow as it is clear what the write is. And also the
function signature is more readable.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230810091510.13006-22-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 drivers/tty/tty_io.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index c0ba994fb1d0..2c4dfcbef725 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -961,11 +961,8 @@ int tty_write_lock(struct tty_struct *tty, bool ndelay)
  * Split writes up in sane blocksizes to avoid
  * denial-of-service type attacks
  */
-static inline ssize_t do_tty_write(
-	ssize_t (*write)(struct tty_struct *, struct file *, const unsigned char *, size_t),
-	struct tty_struct *tty,
-	struct file *file,
-	struct iov_iter *from)
+static inline ssize_t do_tty_write(struct tty_ldisc *ld, struct tty_struct *tty,
+				   struct file *file, struct iov_iter *from)
 {
 	size_t count = iov_iter_count(from);
 	ssize_t ret, written = 0;
@@ -1022,7 +1019,7 @@ static inline ssize_t do_tty_write(
 		if (copy_from_iter(tty->write_buf, size, from) != size)
 			break;
 
-		ret = write(tty, file, tty->write_buf, size);
+		ret = ld->ops->write(tty, file, tty->write_buf, size);
 		if (ret <= 0)
 			break;
 
@@ -1093,7 +1090,7 @@ static ssize_t file_tty_write(struct file *file, struct kiocb *iocb, struct iov_
 	if (!ld->ops->write)
 		ret = -EIO;
 	else
-		ret = do_tty_write(ld->ops->write, tty, file, from);
+		ret = do_tty_write(ld, tty, file, from);
 	tty_ldisc_deref(ld);
 	return ret;
 }