On 2021/08/06 15:35, Hannes Reinecke wrote:
> On 8/6/21 7:11 AM, Damien Le Moal wrote:
>> An iocb aio_reqprio field is 16-bits (u16) but often handled as an int
>> in the block layer. E.g. ioprio_check_cap() takes an int as argument.
>> With such implicit int casting function calls, the upper 16-bits of the
>> int argument may be left uninitialized by the compiler, resulting in
>> invalid values for the IOPRIO_PRIO_CLASS() macro (garbage upper bits)
>> and in an error return for functions such as ioprio_check_cap().
>>
>> Fix this by masking the result of the shift by IOPRIO_CLASS_SHIFT bits
>> in the IOPRIO_PRIO_CLASS() macro. The new macro IOPRIO_CLASS_MASK
>> defines the 3-bits mask for the priority class.
>>
>> While at it, cleanup the following:
>> * Apply the mask IOPRIO_PRIO_MASK to the data argument of the
>> IOPRIO_PRIO_VALUE() macro to ignore upper bits of the data value.
>> * Remove unnecessary parenthesis around fixed values in the macro
>> definitions in include/uapi/linux/ioprio.h.
>> * Update the outdated mention of CFQ in the comment describing priority
>> classes and instead mention BFQ and mq-deadline.
>> * Change the argument name of the IOPRIO_PRIO_CLASS() and
>> IOPRIO_PRIO_DATA() macros from "mask" to "ioprio" to reflect the fact
>> that an IO priority value should be passed rather than a mask.
>> * Change the ioprio_valid() macro into an inline function, adding a
>> check on the maximum value of the class of a priority value as
>> defined by the IOPRIO_CLASS_MAX enum value. Move this function to
>> the kernel side in include/linux/ioprio.h.
>> * Remove the unnecessary "else" after the return statements in
>> task_nice_ioclass().
>>
>> Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
>> ---
>> include/linux/ioprio.h | 15 ++++++++++++---
>> include/uapi/linux/ioprio.h | 19 +++++++++++--------
>> 2 files changed, 23 insertions(+), 11 deletions(-)
>>
>> diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
>> index ef9ad4fb245f..9b3a6d8172b4 100644
>> --- a/include/linux/ioprio.h
>> +++ b/include/linux/ioprio.h
>> @@ -8,6 +8,16 @@
>>
>> #include <uapi/linux/ioprio.h>
>>
>> +/*
>> + * Check that a priority value has a valid class.
>> + */
>> +static inline bool ioprio_valid(unsigned short ioprio)
>
> Wouldn't it be better to use 'u16' here as type, as we're relying on the
> number of bits?
Other functions in block/ioprio.c and in include/linux/ioprio.h use "unsigned
short", so I followed. But many functions, if not most, use "int". This is all a
bit of a mess. I think we need a "typedef ioprio_t u16;" to clean things up. But
there are a lot of places to fix. I can add such patch... Worth it ?
>
>> +{
>> + unsigned short class = IOPRIO_PRIO_CLASS(ioprio);
>> +
>> + return class > IOPRIO_CLASS_NONE && class < IOPRIO_CLASS_MAX;
>> +}
>> +
>> /*
>> * if process has set io priority explicitly, use that. if not, convert
>> * the cpu scheduler nice value to an io priority
>> @@ -25,10 +35,9 @@ static inline int task_nice_ioclass(struct task_struct *task)
>> {
>> if (task->policy == SCHED_IDLE)
>> return IOPRIO_CLASS_IDLE;
>> - else if (task_is_realtime(task))
>> + if (task_is_realtime(task))
>> return IOPRIO_CLASS_RT;
>> - else
>> - return IOPRIO_CLASS_BE;
>> + return IOPRIO_CLASS_BE;
>> }
>>
>> /*
>> diff --git a/include/uapi/linux/ioprio.h b/include/uapi/linux/ioprio.h
>> index 77b17e08b0da..abc40965aa96 100644
>> --- a/include/uapi/linux/ioprio.h
>> +++ b/include/uapi/linux/ioprio.h
>> @@ -5,12 +5,15 @@
>> /*
>> * Gives us 8 prio classes with 13-bits of data for each class
>> */
>> -#define IOPRIO_CLASS_SHIFT (13)
>> +#define IOPRIO_CLASS_SHIFT 13
>> +#define IOPRIO_CLASS_MASK 0x07
>> #define IOPRIO_PRIO_MASK ((1UL << IOPRIO_CLASS_SHIFT) - 1)
>>
>> -#define IOPRIO_PRIO_CLASS(mask) ((mask) >> IOPRIO_CLASS_SHIFT)
>> -#define IOPRIO_PRIO_DATA(mask) ((mask) & IOPRIO_PRIO_MASK)
>> -#define IOPRIO_PRIO_VALUE(class, data) (((class) << IOPRIO_CLASS_SHIFT) | data)
>> +#define IOPRIO_PRIO_CLASS(ioprio) \
>> + (((ioprio) >> IOPRIO_CLASS_SHIFT) & IOPRIO_CLASS_MASK)
>> +#define IOPRIO_PRIO_DATA(ioprio) ((ioprio) & IOPRIO_PRIO_MASK)
>> +#define IOPRIO_PRIO_VALUE(class, data) \
>> + (((class) << IOPRIO_CLASS_SHIFT) | ((data) & IOPRIO_PRIO_MASK))
>>
>> /*
>> * These are the io priority groups as implemented by CFQ. RT is the realtime
>> @@ -23,14 +26,14 @@ enum {
>> IOPRIO_CLASS_RT,
>> IOPRIO_CLASS_BE,
>> IOPRIO_CLASS_IDLE,
>> -};
>>
>> -#define ioprio_valid(mask) (IOPRIO_PRIO_CLASS((mask)) != IOPRIO_CLASS_NONE)
>> + IOPRIO_CLASS_MAX,
>> +};
>>
>> /*
>> * 8 best effort priority levels are supported
>> */
>> -#define IOPRIO_BE_NR (8)
>> +#define IOPRIO_BE_NR 8
>>
>> enum {
>> IOPRIO_WHO_PROCESS = 1,
>> @@ -41,6 +44,6 @@ enum {
>> /*
>> * Fallback BE prioritye@su
>> */
>> -#define IOPRIO_NORM (4)
>> +#define IOPRIO_NORM 4
>>
>> #endif /* _UAPI_LINUX_IOPRIO_H */
>>
> Other than that:
>
> Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
>
> Cheers,
>
> Hannes
>
--
Damien Le Moal
Western Digital Research
