dlm: drop dlm_scand kthread and use timers

Currently the scand kthread acts like a garbage collection for expired
rsbs on toss list, to clean them up after a certain timeout. It triggers
every couple of seconds and iterates over the toss list while holding
ls_rsbtbl_lock for the whole hash bucket iteration.

To reduce the amount of time holding ls_rsbtbl_lock, we now handle the
disposal of expired rsbs using a per-lockspace timer that expires for the
earliest tossed rsb on the lockspace toss queue. This toss queue is
ordered according to the rsb res_toss_time with the earliest tossed rsb
as the first entry. The toss timer will only trylock() necessary locks,
since it is low priority garbage collection, and will rearm the timer
if trylock() fails. If the timer function does not find any expired
rsb's, it rearms the timer with the next earliest expired rsb.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/dlm/recover.c b/fs/dlm/recover.c
index d43189532b14..960a14b95605 100644
--- a/fs/dlm/recover.c
+++ b/fs/dlm/recover.c
@@ -889,6 +889,11 @@ void dlm_clear_toss(struct dlm_ls *ls)
 		list_del(&r->res_rsbs_list);
 		rhashtable_remove_fast(&ls->ls_rsbtbl, &r->res_node,
 				       dlm_rhash_rsb_params);
+
+		/* remove it from the toss queue if its part of it */
+		if (!list_empty(&r->res_toss_q_list))
+			list_del_init(&r->res_toss_q_list);
+
 		free_toss_rsb(r);
 		count++;
 	}