tty: fix up hung_up_tty_read() conversion

commit ddc5fda7456178e2cbc87675b370920d98360daf upstream.

In commit "tty: implement read_iter", I left the read_iter conversion of
the hung up tty case alone, because I incorrectly thought it didn't
matter.

Jiri showed me the errors of my ways, and pointed out the problems with
that incomplete conversion.  Fix it all up.

Reported-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/CAHk-=wh+-rGsa=xruEWdg_fJViFG8rN9bpLrfLz=_yBYh2tBhA@mail.gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index c4596b4..146bd67 100644 (file)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -429,8 +429,7 @@ struct tty_driver *tty_find_polling_driver(char *name, int *line)
 EXPORT_SYMBOL_GPL(tty_find_polling_driver);
 #endif
 
-static ssize_t hung_up_tty_read(struct file *file, char __user *buf,
-                               size_t count, loff_t *ppos)
+static ssize_t hung_up_tty_read(struct kiocb *iocb, struct iov_iter *to)
 {
        return 0;
 }
@@ -502,7 +501,7 @@ static const struct file_operations console_fops = {
 
 static const struct file_operations hung_up_tty_fops = {
        .llseek         = no_llseek,
-       .read           = hung_up_tty_read,
+       .read_iter      = hung_up_tty_read,
        .write_iter     = hung_up_tty_write,
        .poll           = hung_up_tty_poll,
        .unlocked_ioctl = hung_up_tty_ioctl,
@@ -929,8 +928,10 @@ static ssize_t tty_read(struct kiocb *iocb, struct iov_iter *to)
        /* We want to wait for the line discipline to sort out in this
           situation */
        ld = tty_ldisc_ref_wait(tty);
+       if (!ld)
+               return hung_up_tty_read(iocb, to);
        i = -EIO;
-       if (ld && ld->ops->read)
+       if (ld->ops->read)
                i = iterate_tty_read(ld, tty, file, to);
        tty_ldisc_deref(ld);