linux-kernel - Re: [PATCH] kernel/module.c: fix warning about unused nowarn variable

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Date:   Mon, 5 Jun 2017 22:09:24 -0700
From:   Jessica Yu <jeyu@...hat.com>
To:     Corentin Labbe <clabbe.montjoie@...il.com>
Cc:     rusty@...tcorp.com.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/module.c: fix warning about unused nowarn variable

+++ Corentin Labbe [02/06/17 14:05 +0200]:
>This patch fix the following warning:
>kernel/module.c: In function 'add_usage_links':
>kernel/module.c:1653:6: warning: variable 'nowarn' set but not used [-Wunused-but-set-variable]
>  int nowarn;
>
>Signed-off-by: Corentin Labbe <clabbe.montjoie@...il.com>
>---
> kernel/module.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
>diff --git a/kernel/module.c b/kernel/module.c
>index e3e9dbba6a5b..aed902bcb4aa 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -1663,19 +1663,20 @@ static inline void remove_notes_attrs(struct module *mod)
> }
> #endif /* CONFIG_KALLSYMS */
>
>-static void add_usage_links(struct module *mod)
>+static int add_usage_links(struct module *mod)
> {
>+	int ret = 0;
> #ifdef CONFIG_MODULE_UNLOAD
> 	struct module_use *use;
>-	int nowarn;
>
> 	mutex_lock(&module_mutex);
> 	list_for_each_entry(use, &mod->target_list, target_list) {
>-		nowarn = sysfs_create_link(use->target->holders_dir,
>+		ret = sysfs_create_link(use->target->holders_dir,
> 					   &mod->mkobj.kobj, mod->name);

ret will get overwritten with each iteration of the loop; we should return
ret as soon as we hit an error (while making sure we unlock
module_mutex).

> 	}
> 	mutex_unlock(&module_mutex);
> #endif
>+	return ret;
> }
>
> static void del_usage_links(struct module *mod)
>@@ -1798,13 +1799,17 @@ static int mod_sysfs_setup(struct module *mod,
> 	if (err)
> 		goto out_unreg_param;
>
>-	add_usage_links(mod);
>+	err = add_usage_links(mod);
>+	if (err)
>+		goto out_unreg_usage_links;

Small nitpick: could you add an extra newline here?

> 	add_sect_attrs(mod, info);
> 	add_notes_attrs(mod, info);
>
> 	kobject_uevent(&mod->mkobj.kobj, KOBJ_ADD);
> 	return 0;
>
>+out_unreg_usage_links:

Can you rename this to `out_unreg_modinfo_attrs` (to better reflect
what's being done)?

>+	module_remove_modinfo_attrs(mod);
> out_unreg_param:
> 	module_param_sysfs_remove(mod);
> out_unreg_holders:

Thanks,

Jessica