Re: [PATCH v5 3/9] writeback: convert variables to unsigned
From: Greg Thelen
Date: Mon Feb 28 2011 - 18:53:21 EST
On Sun, Feb 27, 2011 at 8:07 AM, Minchan Kim <minchan.kim@xxxxxxxxx> wrote:
> On Fri, Feb 25, 2011 at 01:35:54PM -0800, Greg Thelen wrote:
>> Convert two balance_dirty_pages() page counter variables (nr_reclaimable
>> and nr_writeback) from 'long' to 'unsigned long'.
>> These two variables are used to store results from global_page_state().
>> global_page_state() returns unsigned long and carefully sums per-cpu
>> counters explicitly avoiding returning a negative value.
>> Signed-off-by: Greg Thelen <gthelen@xxxxxxxxxx>
> Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
>> Changelog since v4:
>> - Created this patch for clarity. Previously this patch was integrated within
>> the "writeback: create dirty_info structure" patch.
>> mm/page-writeback.c | 6 ++++--
>> 1 files changed, 4 insertions(+), 2 deletions(-)
>> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
>> index 2cb01f6..4408e54 100644
>> --- a/mm/page-writeback.c
>> +++ b/mm/page-writeback.c
>> @@ -478,8 +478,10 @@ unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
>> static void balance_dirty_pages(struct address_space *mapping,
>> unsigned long write_chunk)
>> - long nr_reclaimable, bdi_nr_reclaimable;
>> - long nr_writeback, bdi_nr_writeback;
>> + unsigned long nr_reclaimable;
>> + long bdi_nr_reclaimable;
>> + unsigned long nr_writeback;
>> + long bdi_nr_writeback;
>> unsigned long background_thresh;
>> unsigned long dirty_thresh;
>> unsigned long bdi_thresh;
> bdi_nr_[reclaimable|writeback] can return negative value?
> When I just look through bdi_stat_sum, it uses *percpu_counter_sum_positive*.
> So I guess it always returns positive value.
> If it is right, could you change it, too?
Yes, I think we can also change bdi_nr_[reclaimable|writeback] to unsigned long.
bdi_stat_sum() and bdi_stat() both call percpu_counter_sum_positive(),
which return a positive number. bdi_stat[_sum]() return s64. Should
we also change bdi_stat[_sum]() to return unsigned long rather than
s64? I would like the return value type to match the type of the
corresponding local variables in balance_dirty_pages(). All current
callers appear to expect bdi_stat[_sum]() to return unsigned long.
> Kind regards,
> Minchan Kim
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