Messages in this thread Patch in this message | | | From | Jiri Slaby <> | Subject | [PATCH 3.12 25/83] writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth() | Date | Mon, 27 Apr 2015 23:31:56 +0200 |
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From: Tejun Heo <tj@kernel.org>
3.12-stable review patch. If anyone has any objections, please let me know.
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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 <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: Jiri Slaby <jslaby@suse.cz> --- 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 9f45f87a5859..d3653325a255 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -943,7 +943,7 @@ 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 -- 2.3.5
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