[RFC dlm/next 06/11] dlm: track reference for lkb_rsb_lookup

[Alexander Aring <aahringo@redhat.com>]

We don't track the reference for lkb_rsb_lookup list. This only probably
works because _request_lock() is sending out a request to a remote node
as this is the lock master as we don't evaluate the return value of
_request_lock() for a potential -EAGAIN. Future patches introduce a new
reference counting model for lkbs that does not require evaluating of
_request_lock() for a potential put. There might be potential issues
because recovery could interact inbetween and changing the lock master.
However we track the reference now if an lkb is part of the
lkb_rsb_lookup list and drop it again when it is deleted.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 fs/dlm/lock.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index 1f4f2d24bef4..b570e9f7cc6f 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -2658,6 +2658,7 @@ static int set_master(struct dlm_rsb *r, struct dlm_lkb *lkb)
 	}
 
 	if (r->res_first_lkid && r->res_first_lkid != lkb->lkb_id) {
+		hold_lkb(lkb);
 		list_add_tail(&lkb->lkb_rsb_lookup, &r->res_lookup);
 		return 1;
 	}
@@ -2700,6 +2701,7 @@ static void process_lookup_list(struct dlm_rsb *r)
 	list_for_each_entry_safe(lkb, safe, &r->res_lookup, lkb_rsb_lookup) {
 		list_del_init(&lkb->lkb_rsb_lookup);
 		_request_lock(r, lkb);
+		dlm_put_lkb(lkb);
 	}
 }
 
@@ -2734,6 +2736,7 @@ static void confirm_master(struct dlm_rsb *r, int error)
 			list_del_init(&lkb->lkb_rsb_lookup);
 			r->res_first_lkid = lkb->lkb_id;
 			_request_lock(r, lkb);
+			dlm_put_lkb(lkb);
 		}
 		break;
 
@@ -2904,6 +2907,8 @@ static int validate_unlock_args(struct dlm_lkb *lkb, struct dlm_args *args)
 				   args->flags & DLM_LKF_CANCEL ?
 				   -DLM_ECANCEL : -DLM_EUNLOCK);
 			unhold_lkb(lkb); /* undoes create_lkb() */
+			/* for lkb_rsb_lookup */
+			dlm_put_lkb(lkb);
 		}
 		/* caller changes -EBUSY to 0 for CANCEL and FORCEUNLOCK */
 		goto out;
-- 
2.43.0