Re: [PATCH 3/6] tty: implement read_iter

Jiri Slaby
2021-01-21T10:55:34Z

On 21. 01. 21, 10:00, Greg Kroah-Hartman wrote:
> From: Linus Torvalds <torvalds@linux-foundation.org>
>
> Now that the ldisc read() function takes kernel pointers, it's fairly
> straightforward to make the tty file operations use .read_iter() instead
> of .read().
>
> That automatically gives us vread() and friends, and also makes it
> possible to do .splice_read() on ttys again.
>
> Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops")
> Reported-by: Oliver Giles <ohw.giles@gmail.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> ---
> drivers/tty/tty_io.c | 36 ++++++++++++++++++------------------
> 1 file changed, 18 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index a34f8bcf875e..8846d3b99845 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
...
> @@ -907,10 +909,10 @@ static int iterate_tty_read(struct tty_ldisc *ld, struct tty_struct *tty, struct
> * read calls may be outstanding in parallel.
> */
>
> -static ssize_t tty_read(struct file *file, char __user *buf, size_t count,
> - loff_t *ppos)
> +static ssize_t tty_read(struct kiocb *iocb, struct iov_iter *to)
> {
> int i;
> + struct file *file = iocb->ki_filp;
> struct inode *inode = file_inode(file);
> struct tty_struct *tty = file_tty(file);
> struct tty_ldisc *ld;
> @@ -923,11 +925,9 @@ static ssize_t tty_read(struct file *file, char __user *buf, size_t count,
> /* 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(file, buf, count, ppos);
> i = -EIO;
> - if (ld->ops->read)
> - i = iterate_tty_read(ld, tty, file, buf, count);
> + if (ld && ld->ops->read)
> + i = iterate_tty_read(ld, tty, file, to);
> tty_ldisc_deref(ld);

Here we have the same problem as in tty_write.

And also the other one with hung_up_tty_read not converted.

thanks,
--
js