Re: [RFC PATCH v3 05/14] mm: add bdi_get_max_bytes() function

[Stefan Roesch <shr@devkernel.io>]

Andrew Morton <akpm@linux-foundation.org> writes:

> On Mon, 24 Oct 2022 12:05:54 -0700 Stefan Roesch <shr@devkernel.io> wrote:
>
>> This adds a function to return the specified value for max_bytes. It
>> converts the stored max_ratio of the bdi to the corresponding bytes
>> value. It introduces the bdi_get_bytes helper function to do the
>> conversion. This is an approximation as it is based on the value that is
>> returned by global_dirty_limits(), which can change. The helper function
>> will also be used by the min_bytes bdi knob.
>>
>> --- a/include/linux/backing-dev.h
>> +++ b/include/linux/backing-dev.h
>> @@ -105,6 +105,7 @@ static inline unsigned long wb_stat_error(void)
>>  /* BDI ratio is expressed as part per 1000 for finer granularity. */
>>  #define BDI_RATIO_SCALE 10
>>
>> +unsigned long long bdi_get_max_bytes(struct backing_dev_info *bdi);
>
> We don't use unsigned long long much.  If you want a 64-bit unsigned,
> use u64?
>

The next version will use u64.

>> +EXPORT_SYMBOL_GPL(bdi_get_max_bytes);
>
> Is this symbol to be used by modules?

The next version will remove the export.