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SubjectRe: [PATCH 5/6] fs-writeback: move nr_pages == 0 logic to one location
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On 09/20/2017 09:36 AM, Jan Kara wrote:
> On Wed 20-09-17 09:05:51, Jens Axboe wrote:
>> On 09/20/2017 08:41 AM, Jan Kara wrote:
>>> On Tue 19-09-17 13:53:06, Jens Axboe wrote:
>>>> Now that we have no external callers of wb_start_writeback(),
>>>> we can move the nr_pages == 0 logic into that function.
>>>>
>>>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>>>
>>> ...
>>>
>>>> +static unsigned long get_nr_dirty_pages(void)
>>>> +{
>>>> + return global_node_page_state(NR_FILE_DIRTY) +
>>>> + global_node_page_state(NR_UNSTABLE_NFS) +
>>>> + get_nr_dirty_inodes();
>>>> +}
>>>> +
>>>> static void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
>>>> bool range_cyclic, enum wb_reason reason)
>>>> {
>>>> @@ -942,6 +953,12 @@ static void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
>>>> return;
>>>>
>>>> /*
>>>> + * If someone asked for zero pages, we write out the WORLD
>>>> + */
>>>> + if (!nr_pages)
>>>> + nr_pages = get_nr_dirty_pages();
>>>> +
>>>
>>> So for 'wb' we have a better estimate of the amount we should write - use
>>> wb_stat_sum(wb, WB_RECLAIMABLE) statistics - that is essentially dirty +
>>> unstable_nfs broken down to bdi_writeback.
>>
>> I don't mind making that change, but I think that should be a separate
>> patch. We're using get_nr_dirty_pages() in existing locations where
>> we have the 'wb', like in wb_check_old_data_flush().
>
> Good point and fully agreed. So you can add:
>
> Reviewed-by: Jan Kara <jack@suse.cz>

Thanks Jan, added. I just sent out the new version, mainly because the
removal or 'nr_pages' changes the later patches a bit. All for the
better, in my opinion.

--
Jens Axboe

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