From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo , Jan Kara , Wu Fengguang , Jens Axboe , Jens Axboe Subject: [PATCH 3.14 16/43] writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth() Date: Fri, 17 Apr 2015 15:28:50 +0200 Message-Id: <20150417132556.707769885@linuxfoundation.org> In-Reply-To: <20150417132556.014766917@linuxfoundation.org> References: <20150417132556.014766917@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tejun Heo commit 7d70e15480c0450d2bfafaad338a32e884fc215e upstream. 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 Acked-by: Jan Kara Cc: Wu Fengguang Cc: Jens Axboe Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- mm/page-writeback.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -943,7 +943,7 @@ 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