linux-kernel - Re: [PATCH v2 3/4] printk/btrfs: Handle more message headers

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Date:   Fri, 11 Nov 2016 12:41:34 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Joe Perches <joe@...ches.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Jason Wessel <jason.wessel@...driver.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, Chris Mason <clm@...com>,
        Josef Bacik <jbacik@...com>, David Sterba <dsterba@...e.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] printk/btrfs: Handle more message headers

On Wed,  9 Nov 2016 13:41:30 +0100
Petr Mladek <pmladek@...e.com> wrote:

> The commit 4bcc595ccd80decb4245096e ("printk: reinstate KERN_CONT for
> printing continuation lines") allows to define more message headers
> for a single message. The motivation is that continuous lines might
> get mixed. Therefore it make sense to define the right log level
> for every piece of a cont line.
> 
> The current btrfs_printk() macros do not support continuous lines
> at the moment. But better be prepared for a custom messages and
> avoid potential "lvl" buffer overflow.
> 
> This patch iterates over the entire message header. It is interested
> only into the message level like the original code.
> 
> This patch also introduces PRINTK_MAX_SINGLE_HEADER_LEN. Three bytes
> are enough for the message level header at the moment. But it used to
> be three, see the commit 04d2c8c83d0e3ac5f ("printk: convert the format
> for KERN_<LEVEL> to a 2 byte pattern").
> 
> Also I fixed the default ratelimit level. It looked very strange
> when it was different from the default log level.
> 
> Signed-off-by: Petr Mladek <pmladek@...e.com>
> ---
>  fs/btrfs/super.c       | 26 +++++++++++++++-----------
>  include/linux/printk.h |  2 ++
>  2 files changed, 17 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 74ed5aae6cea..c083d84eaa32 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -202,27 +202,31 @@ void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function
>  void btrfs_printk(const struct btrfs_fs_info *fs_info, const char *fmt, ...)
>  {
>  	struct super_block *sb = fs_info->sb;
> -	char lvl[4];
> +	char lvl[PRINTK_MAX_SINGLE_HEADER_LEN + 1];
>  	struct va_format vaf;
>  	va_list args;
> -	const char *type = logtypes[4];
> +	const char *type = NULL;
>  	int kern_level;
>  	struct ratelimit_state *ratelimit;
>  
>  	va_start(args, fmt);
>  
> -	kern_level = printk_get_level(fmt);
> -	if (kern_level) {
> +	while ((kern_level = printk_get_level(fmt)) != 0) {
>  		size_t size = printk_skip_level(fmt) - fmt;
> -		memcpy(lvl, fmt,  size);
> -		lvl[size] = '\0';
> +
> +		if (kern_level >= '0' || kern_level <= '7') {

Shouldn't this be kernel_level >= '0' && kern_level <= '7' ?

-- Steve

> +			memcpy(lvl, fmt,  size);
> +			lvl[size] = '\0';
> +			type = logtypes[kern_level - '0'];
> +			ratelimit = &printk_limits[kern_level - '0'];
> +		}
>  		fmt += size;
> -		type = logtypes[kern_level - '0'];
> -		ratelimit = &printk_limits[kern_level - '0'];
> -	} else {
> +	}
> +
> +	if (!type) {
>  		*lvl = '\0';
> -		/* Default to debug output */
> -		ratelimit = &printk_limits[7];
> +		type = logtypes[4];
> +		ratelimit = &printk_limits[4];
>  	}
>