Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
To:     <jeyu@kernel.org>, <rusty@rustcorp.com.au>, <kay.sievers@vrfy.org>,
        <clabbe.montjoie@gmail.com>
CC:     <linux-kernel@vger.kernel.org>,
        "wangxiaogang (F)" <wangxiaogang3@huawei.com>,
        "Zhoukang (A)" <zhoukang7@huawei.com>,
        Mingfangsen <mingfangsen@huawei.com>
From:   Zhiqiang Liu <liuzhiqiang26@huawei.com>
Subject: [PATCH] module: add usage links when calling ref_module func
Message-ID: <8d7aa8b1-73a2-db7a-82c8-06917eddf235@huawei.com>
Date:   Fri, 28 Jun 2019 20:32:18 +0800
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101
 Thunderbird/60.5.0
MIME-Version: 1.0
Content-Type: text/plain; charset="gb18030"
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Zhiqiang Liu <liuzhiqiang26@huawei.com>

Problem: Users can call ref_module func in their modules to construct
relationships with other modules. However, the holders
'/sys/module/<mod-name>/holders' of the target module donot include
the users` module. So lsmod command misses detailed info of 'Used by'.

When load module, the process is given as follows,
load_module()
	-> mod_sysfs_setup()
		-> add_usage_links
	-> do_init_module
		-> mod->init()

add_usage_links func creates holders of target modules linking to
this module. If ref_module is called in mod->init() func, the usage
links cannot be added.

Here, we will add usage link of a to b's holder_dir.

Fixes: 9bea7f239 ("module: fix bne2 "gave up waiting for init of module libcrc32c")
Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
---
 kernel/module.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/module.c b/kernel/module.c
index 80c7c09584cf..11c6aff37b1f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -871,6 +871,11 @@ int ref_module(struct module *a, struct module *b)
 		module_put(b);
 		return err;
 	}
+
+	err = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);
+	if (err)
+		return err;
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(ref_module);
-- 
2.19.1