linux-kernel - Re: [PATCH net-next 3/5] netconsole: append msgid to sysdata

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Message-ID: <aEmhA0QoZy3LbAu+@gmail.com>
Date: Wed, 11 Jun 2025 08:30:11 -0700
From: Breno Leitao <leitao@...ian.org>
To: Gustavo Luiz Duarte <gustavold@...il.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Shuah Khan <shuah@...nel.org>, Simon Horman <horms@...nel.org>,
	Jonathan Corbet <corbet@....net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH net-next 3/5] netconsole: append msgid to sysdata

On Wed, Jun 11, 2025 at 07:36:05AM -0700, Gustavo Luiz Duarte wrote:
> Add msgcounter to the netconsole_target struct to generate message IDs.
> If the msgid_enabled attribute is true, increment msgcounter and append
> msgid=<msgcounter> to sysdata buffer before sending the message.
> 
> Signed-off-by: Gustavo Luiz Duarte <gustavold@...il.com>
> ---
>  drivers/net/netconsole.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> index 813f50abaf9f..34b61e299eeb 100644
> --- a/drivers/net/netconsole.c
> +++ b/drivers/net/netconsole.c
> @@ -155,6 +155,8 @@ struct netconsole_target {
>  	size_t			userdata_length;
>  	/* bit-wise with sysdata_feature bits */
>  	u32			sysdata_fields;
> +	/* protected by target_list_lock */
> +	u32			msgcounter;
>  #endif
>  	struct netconsole_target_stats stats;
>  	bool			enabled;
> @@ -1345,13 +1347,21 @@ static int sysdata_append_release(struct netconsole_target *nt, int offset)
>  			 init_utsname()->release);
>  }
>  
> +static int sysdata_append_msgid(struct netconsole_target *nt, int offset)
> +{
> +	nt->msgcounter++;

This will eventually wrap. I am wondering if you should use the
overflow.h helpers to avoid warnings in UBSAN and friends.

Quick glanced over that filed, I found:

	/**
	* wrapping_add() - Intentionally perform a wrapping addition
	* @type: type for result of calculation
	* @a: first addend
	* @b: second addend
	*
	* Return the potentially wrapped-around addition without
	* tripping any wrap-around sanitizers that may be enabled.
	*/

> +	return scnprintf(&nt->extradata_complete[offset],
> +			 MAX_EXTRADATA_ENTRY_LEN, " msgid=%u\n",
> +			 nt->msgcounter);
> +}
> +
>  /*
>   * prepare_extradata - append sysdata at extradata_complete in runtime
>   * @nt: target to send message to
>   */
>  static int prepare_extradata(struct netconsole_target *nt)
>  {
> -	u32 fields = SYSDATA_CPU_NR | SYSDATA_TASKNAME;
> +	u32 fields = SYSDATA_CPU_NR | SYSDATA_TASKNAME | SYSDATA_MSGID;

This might be gone now, according to your last patch.,

LGTM.