From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH block/for-4.0-fixes] writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth() Date: Wed, 4 Mar 2015 10:37:43 -0500 Message-ID: <20150304153743.GH3122@htj.duckdns.org> References: <20150304152243.GG3122@htj.duckdns.org> <20150304153050.GA1249@quack.suse.cz> <54F72567.3060406@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , Wu Fengguang , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org To: Jens Axboe Return-path: Content-Disposition: inline In-Reply-To: <54F72567.3060406@kernel.dk> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org 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 Acked-by: Jan Kara Cc: Wu Fengguang Cc: Jens Axboe 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 -- 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