lightnvm: pblk: delete writer kick timer before stopping thread

Unless we delete the timer that wakes up the write thread
before we stop the thread we risk re-starting the thread, so
delete the timer first.
Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Reviewed-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-init.c

@@ -912,9 +912,9 @@ static void pblk_writer_stop(struct pblk *pblk)
 	WARN(pblk_rb_sync_count(&pblk->rwb),
 			"Stopping not fully synced write buffer\n");
 
+	del_timer_sync(&pblk->wtimer);
 	if (pblk->writer_ts)
 		kthread_stop(pblk->writer_ts);
-	del_timer(&pblk->wtimer);
 }
 
 static void pblk_free(struct pblk *pblk)