linux-kernel - Re: [PATCH 3/6] tty: implement read

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Message-ID: <72c5fa0a-b0e2-740a-54d1-07e806a53024@kernel.org>
Date:   Thu, 21 Jan 2021 11:44:57 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-serial@...r.kernel.org
Cc:     hch@....de, viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org,
        ohw.giles@...il.com, r.karszniewicz@...tec.de,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 3/6] tty: implement read_iter

On 21. 01. 21, 10:00, Greg Kroah-Hartman wrote:
> From: Linus Torvalds <torvalds@...ux-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@...il.com>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Signed-off-by: Linus Torvalds <torvalds@...ux-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