writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth()
authorTejun Heo <tj@kernel.org>
Wed, 4 Mar 2015 15:37:43 +0000 (10:37 -0500)
committerBen Hutchings <ben@decadent.org.uk>
Sat, 9 May 2015 22:16:30 +0000 (23:16 +0100)
commit 7d70e15480c0450d2bfafaad338a32e884fc215e upstream.

global_update_bandwidth() uses static variable update_time as the
timestamp for the last update but forgets to initialize it to

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>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

index aad22aa..98cd090 100644 (file)
@@ -726,7 +726,7 @@ 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