On Wed 04-03-15 10:22:43, Tejun Heo wrote:
> global_update_bandwidth() uses static variable update_time as the
> timestamp for the last update but forgets to initialize it to
> INITIALIZE_JIFFIES.
>
> This means that global_dirty_limit will be 5 mins into the future on
> 32bit and some large amount jiffies into the past on 64bit. This
> isn't critical as the only effect is that global_dirty_limit won't be
> updated for the first 5 mins after booting on 32bit machines,
> especially given the auxiliary nature of global_dirty_limit's role -
> protecting against global dirty threshold's sudden dips; however, it
> does lead to unintended suboptimal behavior. Fix it.
Looks good. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> mm/page-writeback.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -922,7 +922,7 @@ static void global_update_bandwidth(unsi
> unsigned long now)
> {
> static DEFINE_SPINLOCK(dirty_lock);
> - static unsigned long update_time;
> + static unsigned long update_time = INITIAL_JIFFIES;
>
> /*
> * check locklessly first to optimize away locking for the most time
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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