Re: [PATCH block/for-4.0-fixes] writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth()

From: Jens Axboe
Date: Wed Mar 04 2015 - 10:32:00 EST


On 03/04/2015 08:30 AM, Jan Kara wrote:
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>

We should add that it fixes c42843f2f0bbc (from 2011!) as well.

--
Jens Axboe

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