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

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Message-ID: <77c2ef52-960b-f4d5-9de7-f4a1a4a6e376@arm.com>
Date:   Mon, 15 Mar 2021 09:58:24 +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 3/15/21 9:40 AM, Lukasz Luba wrote:
> 
> 
> 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------------------------------
> 

I've check that label and probably not easy to modify it
and put conditional there. So probably you would have to
call everything here (not jumping to label):

ida_simple_remove(&thermal_cdev_ida, cdev->id);
kfree(cdev);
return ERR_PTR(-_ENOMEM);


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