From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Tejun Heo , Wu Fengguang , Jens Axboe , Jens Axboe , Zefan Li Subject: [PATCH 3.4 123/172] writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth() Date: Tue, 16 Jun 2015 16:36:17 +0800 Message-Id: <1434443826-4929-123-git-send-email-lizf@kernel.org> In-Reply-To: <1434443587-4599-1-git-send-email-lizf@kernel.org> References: <1434443587-4599-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: From: Tejun Heo 3.4.108-rc1 review patch. If anyone has any objections, please let me know. ------------------ 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: Zefan Li --- mm/page-writeback.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 057884c..b747dcd 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -831,7 +831,7 @@ static void global_update_bandwidth(unsigned long thresh, 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 -- 1.9.1