Re: [PATCH net-next v4 3/4] netconsole: Attach cmdline target to dynamic target

[Joel Becker <jlbec@evilplan.org>]

On Thu, Oct 12, 2023 at 04:14:00AM -0700, Breno Leitao wrote:
> Enable the attachment of a dynamic target to the target created during
> boot time. The boot-time targets are named as "cmdline\d", where "\d" is
> a number starting at 0.
> 
> If the user creates a dynamic target named "cmdline0", it will attach to
> the first target created at boot time (as defined in the
> `netconsole=...` command line argument). `cmdline1` will attach to the
> second target and so forth.
> 
> If there is no netconsole target created at boot time, then, the target
> name could be reused.
> 
> Relevant design discussion:
> https://lore.kernel.org/all/ZRWRal5bW93px4km@gmail.com/
> 
> Suggested-by: Joel Becker <jlbec@evilplan.org>
> Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Joel Becker <jlbec@evilplan.org>

> ---
>  drivers/net/netconsole.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> index e153bce4dee4..6e14ba5e06c8 100644
> --- a/drivers/net/netconsole.c
> +++ b/drivers/net/netconsole.c
> @@ -629,6 +629,23 @@ static const struct config_item_type netconsole_target_type = {
>  	.ct_owner		= THIS_MODULE,
>  };
>  
> +static struct netconsole_target *find_cmdline_target(const char *name)
> +{
> +	struct netconsole_target *nt, *ret = NULL;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&target_list_lock, flags);
> +	list_for_each_entry(nt, &target_list, list) {
> +		if (!strcmp(nt->item.ci_name, name)) {
> +			ret = nt;
> +			break;
> +		}
> +	}
> +	spin_unlock_irqrestore(&target_list_lock, flags);
> +
> +	return ret;
> +}
> +
>  /*
>   * Group operations and type for netconsole_subsys.
>   */
> @@ -639,6 +656,17 @@ static struct config_item *make_netconsole_target(struct config_group *group,
>  	struct netconsole_target *nt;
>  	unsigned long flags;
>  
> +	/* Checking if a target by this name was created at boot time.  If so,
> +	 * attach a configfs entry to that target.  This enables dynamic
> +	 * control.
> +	 */
> +	if (!strncmp(name, NETCONSOLE_PARAM_TARGET_PREFIX,
> +		     strlen(NETCONSOLE_PARAM_TARGET_PREFIX))) {
> +		nt = find_cmdline_target(name);
> +		if (nt)
> +			return &nt->item;
> +	}
> +
>  	nt = alloc_and_init();
>  	if (!nt)
>  		return ERR_PTR(-ENOMEM);
> -- 
> 2.34.1
> 

-- 

"Nobody loves me,
 Nobody seems to care.
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			http://www.jlbec.org/
			jlbec@evilplan.org