linux-kernel - Re: [PATCH] block: uapi: Fix compliation warning of using IOPRIO_PRIO

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Message-ID: <1543faf3-d721-4e35-b467-08726a7ba27e@kernel.org>
Date: Tue, 9 Jul 2024 13:50:48 +0900
From: Damien Le Moal <dlemoal@...nel.org>
To: Zhiguo Niu <niuzhiguo84@...il.com>, axboe@...nel.dk,
 Christoph Hellwig <hch@....de>
Cc: Bart Van Assche <bvanassche@....org>, linux-kernel@...r.kernel.org,
 Zhiguo Niu <zhiguo.niu@...soc.com>, ke.wang@...soc.com
Subject: Re: [PATCH] block: uapi: Fix compliation warning of using
 IOPRIO_PRIO_DATA

On 7/9/24 12:27, Zhiguo Niu wrote:
> kindly ping...
> 
> Bart Van Assche <bvanassche@....org> 于2024年6月1日周六 04:13写道：
> 
> 
>>
>> On 5/31/24 04:31, Zhiguo Niu wrote:
>>> Generally, the input of IOPRIO_PRIO_DATA has 16 bits. If use format "%d"
>>> to printk IOPRIO_PRIO_DATA, there will be the following warning or error.
>>>
>>> fs/f2fs/sysfs.c:348:31: warning: format ‘%d’ expects argument of type ‘int’, but argument 4 has type ‘long unsigned int’ [-Wformat=]
>>>     return sysfs_emit(buf, "%s,%d\n",
>>>                                ~^
>>>                                %ld
>>>
>>> This is because the output of IOPRIO_PRIO_DATA is converted to "UL" from
>>> IOPRIO_PRIO_MASK, which is not reasonable. unsigned int is more suitable.
>>>
>>> Signed-off-by: Zhiguo Niu <zhiguo.niu@...soc.com>
>>> ---
>>>   include/uapi/linux/ioprio.h | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
>>> index bee2bdb0..9ead07f 100644
>>> --- a/include/uapi/linux/ioprio.h
>>> +++ b/include/uapi/linux/ioprio.h
>>> @@ -11,7 +11,7 @@
>>>   #define IOPRIO_CLASS_SHIFT  13
>>>   #define IOPRIO_NR_CLASSES   8
>>>   #define IOPRIO_CLASS_MASK   (IOPRIO_NR_CLASSES - 1)
>>> -#define IOPRIO_PRIO_MASK     ((1UL << IOPRIO_CLASS_SHIFT) - 1)
>>> +#define IOPRIO_PRIO_MASK     ((1U << IOPRIO_CLASS_SHIFT) - 1)
>>>
>>>   #define IOPRIO_PRIO_CLASS(ioprio)   \
>>>       (((ioprio) >> IOPRIO_CLASS_SHIFT) & IOPRIO_CLASS_MASK)
>>
>> This change is safe even if the mask is applied to an expression with more bits
>> than an int because of the integer promotion rules. Hence:
>>
>> Reviewed-by: Bart Van Assche <bvanassche@....org>

Looks good to me but I think this needs a Fixes tag and Cc-stable.

-- 
Damien Le Moal
Western Digital Research