linux-kernel - Re: [PATCH] [v3] module: don't ignore sysfs_create

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Date: Mon, 08 Apr 2024 10:02:15 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>,
 "Arnd Bergmann" <arnd@...nel.org>
Cc: "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
 "Luis Chamberlain" <mcgrof@...nel.org>, linux-modules@...r.kernel.org,
 "Rafael J . Wysocki" <rafael@...nel.org>, "Jens Axboe" <axboe@...nel.dk>,
 "Ricardo B. Marliere" <ricardo@...liere.net>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v3] module: don't ignore sysfs_create_link() failures

On Tue, Mar 26, 2024, at 16:29, Andy Shevchenko wrote:
> On Tue, Mar 26, 2024 at 03:57:18PM +0100, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@...db.de>
>> 
>> The sysfs_create_link() return code is marked as __must_check, but the
>> module_add_driver() function tries hard to not care, by assigning the
>> return code to a variable. When building with 'make W=1', gcc still
>> warns because this variable is only assigned but not used:
>> 
>> drivers/base/module.c: In function 'module_add_driver':
>> drivers/base/module.c:36:6: warning: variable 'no_warn' set but not used [-Wunused-but-set-variable]
>> 
>> Rework the code to properly unwind and return the error code to the
>> caller. My reading of the original code was that it tries to
>> not fail when the links already exist, so keep ignoring -EEXIST
>> errors.
>
>> Cc: Luis Chamberlain <mcgrof@...nel.org>
>> Cc: linux-modules@...r.kernel.org
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
>
> Wondering if you can move these to be after --- to avoid polluting commit
> message. This will have the same effect and be archived on lore. But on
> pros side it will unload the commit message(s) from unneeded noise.

Done

>
>> +	error = module_add_driver(drv->owner, drv);
>> +	if (error) {
>> +		printk(KERN_ERR "%s: failed to create module links for %s\n",
>> +			__func__, drv->name);
>
> What's wrong with pr_err()? Even if it's not a style used, in a new pieces of
> code this can be improved beforehand. So, we will reduce a technical debt, and
> not adding to it.

I think that would be more confusing, and would rather keep the
style consistent. There is no practical difference here.

>> +int module_add_driver(struct module *mod, struct device_driver *drv)
>>  {
>>  	char *driver_name;
>> -	int no_warn;
>> +	int ret;
>
> I would move it...
>
>>  	struct module_kobject *mk = NULL;
>
> ...to be here.

Done

     Arnd