linux-kernel - Re: [PATCH 2/3] netconsole: Attach cmdline target to dynamic target

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Message-ID: <ZR3E1TLE+BFuctsx@google.com>
Date:   Wed, 4 Oct 2023 13:02:29 -0700
From:   Joel Becker <jlbec@...lplan.org>
To:     Breno Leitao <leitao@...ian.org>
Cc:     kuba@...nel.org, davem@...emloft.net, pabeni@...hat.com,
        Eric Dumazet <edumazet@...gle.com>, hch@....de,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        horms@...nel.org
Subject: Re: [PATCH 2/3] netconsole: Attach cmdline target to dynamic target

On Mon, Oct 02, 2023 at 08:53:48AM -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@...lplan.org>
> Signed-off-by: Breno Leitao <leitao@...ian.org>
> ---
>  drivers/net/netconsole.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> index b68456054a0c..6235f56dc652 100644
> --- a/drivers/net/netconsole.c
> +++ b/drivers/net/netconsole.c
> @@ -685,6 +685,23 @@ 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.
>   */
> @@ -695,6 +712,13 @@ static struct config_item *make_netconsole_target(struct config_group *group,
>  	struct netconsole_target *nt;
>  	unsigned long flags;
>  
> +	/* Checking if there is a target created populated at boot time */

Perhaps a little clearer:

```
       /* 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, DEFAULT_TARGET_NAME, strlen(DEFAULT_TARGET_NAME))) {
> +		nt = find_cmdline_target(name);
> +		if (nt)
> +			return &nt->item;
> +	}
> +

Thanks,
Joel

-- 

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