From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH block/for-4.0-fixes] writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth() Date: Wed, 4 Mar 2015 16:30:50 +0100 Message-ID: <20150304153050.GA1249@quack.suse.cz> References: <20150304152243.GG3122@htj.duckdns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jens Axboe , Wu Fengguang , Jan Kara , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org To: Tejun Heo Return-path: Content-Disposition: inline In-Reply-To: <20150304152243.GG3122@htj.duckdns.org> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org 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 Honza > > Signed-off-by: Tejun Heo > Cc: Wu Fengguang > Cc: Jan Kara > Cc: Jens Axboe > Cc: stable@vger.kernel.org > --- > 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 SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org