Commit 8da10cce authored Oct 13, 2017 by Javier González Committed by Jens Axboe Oct 13, 2017

lightnvm: pblk: avoid being reported as hung on rated GC



The amount of GC I/O on the write buffer is managed by the rate-limiter,
which is calculated as a function of the number of available free
blocks. When reaching the stable point, we risk having scheduled more
I/Os for GC than are allowed on the write buffer. This would result on
the GC semaphore balancing the outstanding read GC I/Os to be reported
as "hung", though the behavior is normal.

Solve this by allowing to schedule when we detect that the read GC path
is not moving forward.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 8bd40020

drivers/lightnvm/pblk-gc.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -218,7 +218,13 @@ static void pblk_gc_line_prepare_ws(struct work_struct *work)
		gc_rq_ws->line = line;
		gc_rq_ws->priv = gc_rq;

		down(&gc->gc_sem);
		/* The write GC path can be much slower than the read GC one due to
		* the budget imposed by the rate-limiter. Balance in case that we get
		* back pressure from the write GC path.
		*/
		while (down_timeout(&gc->gc_sem, msecs_to_jiffies(30000)))
		io_schedule();

		kref_get(&line->ref);

		INIT_WORK(&gc_rq_ws->ws, pblk_gc_line_ws);