writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth()

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: c42843f2f0 ("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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This commit is contained in:

Tejun Heo

2015-03-04 10:37:43 -05:00

committed by

Greg Kroah-Hartman

parent dfb06c8557

commit f16678367d

1 changed files with 1 additions and 1 deletions

									
										mm/page-writeback.c
									
		+1
		-1
	
												View File
												
				@@ -858,7 +858,7 @@ 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