linux-kernel - Re: [PATCH 3/4] kmod: Return directly if module name is empty in request

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Date:   Sat, 18 Apr 2020 13:58:45 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Luis Chamberlain <mcgrof@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Shuah Khan <shuah@...nel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH 3/4] kmod: Return directly if module name is empty in
 request_module()

On 04/18/2020 01:48 PM, Luis Chamberlain wrote:
> On Fri, Apr 17, 2020 at 11:45 PM Luis Chamberlain <mcgrof@...nel.org> wrote:
>> On Sat, Apr 18, 2020 at 01:19:59PM +0800, Tiezhu Yang wrote:
>>> If module name is empty, it is better to return directly at the beginning
>>> of request_module() without doing the needless call_modprobe() operation.
>>>
>>> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
>>> ---
>>>   kernel/kmod.c | 5 +++++
>>>   1 file changed, 5 insertions(+)
>>>
>>> diff --git a/kernel/kmod.c b/kernel/kmod.c
>>> index 3cd075c..5851444 100644
>>> --- a/kernel/kmod.c
>>> +++ b/kernel/kmod.c
>>> @@ -28,6 +28,8 @@
>>>
>>>   #include <trace/events/module.h>
>>>
>>> +#define MODULE_NOT_FOUND 256
>>> +
>>>   /*
>>>    * Assuming:
>>>    *
>>> @@ -144,6 +146,9 @@ int __request_module(bool wait, const char *fmt, ...)
>>>        if (ret >= MODULE_NAME_LEN)
>>>                return -ENAMETOOLONG;
>>>
>>> +     if (strlen(module_name) == 0)
>>> +             return MODULE_NOT_FOUND;
>> I'd rather we just use something standard like -EINVAL.
>> What do we return if its not found? Then use that value.
> Also, are we testing for this condition yet? If not can we add one?

Yes, kmod_test_0001_driver() in tools/testing/selftests/kmod/kmod.sh tests
this case and expects result MODULE_NOT_FOUND which is 256.