linux-kernel - Re: [PATCH v2] module: Add support for default value for module async

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Message-ID: <20220621202558.jmvn2kozz44e2elg@ava.usersys.com>
Date:   Tue, 21 Jun 2022 21:25:58 +0100
From:   Aaron Tomlin <atomlin@...hat.com>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Jonathan Corbet <corbet@....net>,
        Luis Chamberlain <mcgrof@...nel.org>, kernel-team@...roid.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-modules@...r.kernel.org
Subject: Re: [PATCH v2] module: Add support for default value for module
 async_probe

On Fri 2022-06-03 18:01 -0700, Saravana Kannan wrote:
> Add a module.async_probe kernel command line option that allows enabling
> async probing for all modules. When this command line option is used,
> there might still be some modules for which we want to explicitly force
> synchronous probing, so extend <modulename>.async_probe to take an
> optional bool input so that async probing can be disabled for a specific
> module.
> 
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> ---
> v1->v2:
> - Updated the documentation to capture all the details/changes.
> 
>  Documentation/admin-guide/kernel-parameters.txt | 17 +++++++++++++++--
>  kernel/module/main.c                            | 11 ++++++++++-
>  2 files changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 710b52d87bdd..5174a08e20b0 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1147,8 +1147,12 @@
>  	nopku		[X86] Disable Memory Protection Keys CPU feature found
>  			in some Intel CPUs.
>  
> -	<module>.async_probe [KNL]
> -			Enable asynchronous probe on this module.
> +	<module>.async_probe[=<bool>] [KNL]
> +			If no <bool> value is specified or if the value
> +			specified is not a valid <bool>, enable asynchronous
> +			probe on this module.  Otherwise, enable/disable
> +			asynchronous probe on this module as indicated by the
> +			<bool> value. See also: module.async_probe
>  
>  	early_ioremap_debug [KNL]
>  			Enable debug messages in early_ioremap support. This
> @@ -3201,6 +3205,15 @@
>  			log everything. Information is printed at KERN_DEBUG
>  			so loglevel=8 may also need to be specified.
>  
> +	module.async_probe=<bool>
> +			[KNL] When set to true, modules will use async probing
> +			by default. To enable/disable async probing for a
> +			specific module, use the module specific control that
> +			is documented under <module>.async_probe. When both
> +			module.async_probe and <module>.async_probe are
> +			specified, <module>.async_probe takes precedence for
> +			the specific module.
> +
>  	module.sig_enforce
>  			[KNL] When CONFIG_MODULE_SIG is set, this means that
>  			modules without (valid) signatures will fail to load.
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index fed58d30725d..47085795f037 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -2410,6 +2410,12 @@ static void do_free_init(struct work_struct *w)
>  	}
>  }
>  
> +#undef MODULE_PARAM_PREFIX
> +#define MODULE_PARAM_PREFIX "module."
> +/* Default value for module->async_probe_requested */
> +static bool async_probe;
> +module_param(async_probe, bool, 0644);
> +
>  /*
>   * This is where the real work happens.
>   *
> @@ -2630,7 +2636,8 @@ static int unknown_module_param_cb(char *param, char *val, const char *modname,
>  	int ret;
>  
>  	if (strcmp(param, "async_probe") == 0) {
> -		mod->async_probe_requested = true;
> +		if (strtobool(val, &mod->async_probe_requested))
> +			mod->async_probe_requested = true;
>  		return 0;
>  	}
>  
> @@ -2797,6 +2804,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
>  	if (err)
>  		goto bug_cleanup;
>  
> +	mod->async_probe_requested = async_probe;
> +
>  	/* Module is ready to execute: parsing args may do that. */
>  	after_dashes = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
>  				  -32768, 32767, mod,
> -- 
> 2.36.1.255.ge46751e96f-goog

Reviewed-by: Aaron Tomlin <atomlin@...hat.com>

-- 
Aaron Tomlin