linux-kernel - Re: [PATCH 04/15] tty: n_tty: invert the condition in copy_from_read

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Message-ID: <2f8f7e-d0bd-b8c3-a8b8-d14fd0221e4d@linux.intel.com>
Date:   Tue, 19 Sep 2023 12:54:31 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
cc:     gregkh@...uxfoundation.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/15] tty: n_tty: invert the condition in
 copy_from_read_buf()

On Tue, 19 Sep 2023, Jiri Slaby (SUSE) wrote:

> Make "no numbers available" a fast quit from the function. And do the

Did you really intend to write "numbers" and not e.g. characters?

The change itself looks good,

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

-- 
 i.

> heavy work outside the 'if'. This makes the code more understandable and
> conforming to the common kernel coding style.
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> ---
>  drivers/tty/n_tty.c | 38 ++++++++++++++++++++------------------
>  1 file changed, 20 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
> index 6a112910c058..922fb61b587a 100644
> --- a/drivers/tty/n_tty.c
> +++ b/drivers/tty/n_tty.c
> @@ -1966,24 +1966,26 @@ static bool copy_from_read_buf(const struct tty_struct *tty, u8 **kbp,
>  	size_t tail = MASK(ldata->read_tail);
>  
>  	n = min3(head - ldata->read_tail, N_TTY_BUF_SIZE - tail, *nr);
> -	if (n) {
> -		u8 *from = read_buf_addr(ldata, tail);
> -		memcpy(*kbp, from, n);
> -		is_eof = n == 1 && *from == EOF_CHAR(tty);
> -		tty_audit_add_data(tty, from, n);
> -		zero_buffer(tty, from, n);
> -		smp_store_release(&ldata->read_tail, ldata->read_tail + n);
> -		/* Turn single EOF into zero-length read */
> -		if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
> -		    (head == ldata->read_tail))
> -			return false;
> -		*kbp += n;
> -		*nr -= n;
> -
> -		/* If we have more to copy, let the caller know */
> -		return head != ldata->read_tail;
> -	}
> -	return false;
> +	if (!n)
> +		return false;
> +
> +	u8 *from = read_buf_addr(ldata, tail);
> +	memcpy(*kbp, from, n);
> +	is_eof = n == 1 && *from == EOF_CHAR(tty);
> +	tty_audit_add_data(tty, from, n);
> +	zero_buffer(tty, from, n);
> +	smp_store_release(&ldata->read_tail, ldata->read_tail + n);
> +
> +	/* Turn single EOF into zero-length read */
> +	if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
> +	    head == ldata->read_tail)
> +		return false;
> +
> +	*kbp += n;
> +	*nr -= n;
> +
> +	/* If we have more to copy, let the caller know */
> +	return head != ldata->read_tail;
>  }
>  
>  /**
>