Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Wed, 4 Mar 2015 10:37:43 -0500 | From | Tejun Heo <> | Subject | [PATCH block/for-4.0-fixes] writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth() |
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Subject: writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth()
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.
Fixes: c42843f2f0bb ("writeback: introduce smoothed global dirty limit") Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Jan Kara <jack@suse.cz> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: stable@vger.kernel.org --- Added the "fixes" tag. Jens, can you please route this one?
Thanks.
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
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