netdev - Re: [PATCH v2 1/5] thermal/drivers/core: Use a char pointer for the cooling device name

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Date:   Mon, 15 Mar 2021 09:40:06 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Jiri Pirko <jiri@...dia.com>, Ido Schimmel <idosch@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Amit Kucheria <amitk@...nel.org>,
        "open list:MELLANOX ETHERNET SWITCH DRIVERS" <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] thermal/drivers/core: Use a char pointer for the
 cooling device name



On 3/12/21 9:01 PM, Daniel Lezcano wrote:
> On 12/03/2021 19:49, Lukasz Luba wrote:
>>
>>
>> On 3/12/21 5:03 PM, Daniel Lezcano wrote:
>>> We want to have any kind of name for the cooling devices as we do no
>>> longer want to rely on auto-numbering. Let's replace the cooling
>>> device's fixed array by a char pointer to be allocated dynamically
>>> when registering the cooling device, so we don't limit the length of
>>> the name.
>>>
>>> Rework the error path at the same time as we have to rollback the
>>> allocations in case of error.
>>>
>>> Tested with a dummy device having the name:
>>>    "Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch"
>>>
>>> A village on the island of Anglesey (Wales), known to have the longest
>>> name in Europe.
>>>
>>> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
>>> ---
>>>    .../ethernet/mellanox/mlxsw/core_thermal.c    |  2 +-
>>>    drivers/thermal/thermal_core.c                | 38 +++++++++++--------
>>>    include/linux/thermal.h                       |  2 +-
>>>    3 files changed, 24 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c
>>> b/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c
>>> index bf85ce9835d7..7447c2a73cbd 100644
>>> --- a/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c
>>> +++ b/drivers/net/ethernet/mellanox/mlxsw/core_thermal.c
>>> @@ -141,7 +141,7 @@ static int mlxsw_get_cooling_device_idx(struct
>>> mlxsw_thermal *thermal,
>>>        /* Allow mlxsw thermal zone binding to an external cooling
>>> device */
>>>        for (i = 0; i < ARRAY_SIZE(mlxsw_thermal_external_allowed_cdev);
>>> i++) {
>>>            if (strnstr(cdev->type, mlxsw_thermal_external_allowed_cdev[i],
>>> -                sizeof(cdev->type)))
>>> +                strlen(cdev->type)))
>>>                return 0;
>>>        }
>>>    diff --git a/drivers/thermal/thermal_core.c
>>> b/drivers/thermal/thermal_core.c
>>> index 996c038f83a4..9ef8090eb645 100644
>>> --- a/drivers/thermal/thermal_core.c
>>> +++ b/drivers/thermal/thermal_core.c
>>> @@ -960,10 +960,7 @@ __thermal_cooling_device_register(struct
>>> device_node *np,
>>>    {
>>>        struct thermal_cooling_device *cdev;
>>>        struct thermal_zone_device *pos = NULL;
>>> -    int result;
>>> -
>>> -    if (type && strlen(type) >= THERMAL_NAME_LENGTH)
>>> -        return ERR_PTR(-EINVAL);
>>> +    int ret;
>>>          if (!ops || !ops->get_max_state || !ops->get_cur_state ||
>>>            !ops->set_cur_state)
>>> @@ -973,14 +970,17 @@ __thermal_cooling_device_register(struct
>>> device_node *np,
>>>        if (!cdev)
>>>            return ERR_PTR(-ENOMEM);
>>>    -    result = ida_simple_get(&thermal_cdev_ida, 0, 0, GFP_KERNEL);
>>> -    if (result < 0) {
>>> -        kfree(cdev);
>>> -        return ERR_PTR(result);
>>> +    ret = ida_simple_get(&thermal_cdev_ida, 0, 0, GFP_KERNEL);
>>> +    if (ret < 0)
>>> +        goto out_kfree_cdev;
>>> +    cdev->id = ret;
>>> +
>>> +    cdev->type = kstrdup(type ? type : "", GFP_KERNEL);
>>> +    if (!cdev->type) {
>>> +        ret = -ENOMEM;
>>
>> Since we haven't called the device_register() yet, I would call here:
>> kfree(cdev);
>> and then jump
> 
> I'm not sure to understand, we have to remove the ida, no ?

Yes, we have to remove 'ida' and you jump to that label:
goto out_ida_remove;
but under that label, there is no 'put_device()'.
We could have here, before the 'goto', a simple kfree, which
should be safe, since we haven't called the device_register() yet.
Something like:

--------8<------------------------------
cdev->type = kstrdup(type ? type : "", GFP_KERNEL);
if (!cdev->type) {
	ret = -ENOMEM;
	kfree(cdev);
	goto out_ida_remove;
}

-------->8------------------------------


> 
>> Other than that, LGTM
>>
>> Reviewed-by: Lukasz Luba <lukasz.luba@....com>
>>
>> Regards,
>> Lukasz
> 
>