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

[Jiri Slaby]

On 21. 01. 21, 10:00, Greg Kroah-Hartman wrote:
> From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> ---
>   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