[Ocfs2-devel] [PATCH] ocfs2/dlm: remove potential deadlock -V3

[Wengang Wang]

When we need to take both dlm_domain_lock and dlm->spinlock, we should take
them in order of: dlm_domain_lock then dlm->spinlock.

There is pathes disobey this order. That is calling dlm_lockres_put() with
dlm->spinlock held in dlm_run_purge_list. dlm_lockres_put() calls dlm_put() at
the ref and dlm_put() locks on dlm_domain_lock.

Fix:
Don't grab/put the dlm when the initialising/releasing lockres.
That grab is not required because we don't call dlm_unregister_domain()
based on refcount.

Signed-off-by: Wengang Wang <wen.gang.wang at oracle.com>
---
 fs/ocfs2/dlm/dlmmaster.c |    4 ----
 1 file changed, 4 deletions(-)

diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 94b97fc..0fe7c4d 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -511,8 +511,6 @@ static void dlm_lockres_release(struct kref *kref)
 
 	atomic_dec(&dlm->res_cur_count);
 
-	dlm_put(dlm);
-
 	if (!hlist_unhashed(&res->hash_node) ||
 	    !list_empty(&res->granted) ||
 	    !list_empty(&res->converting) ||
@@ -585,8 +583,6 @@ static void dlm_init_lockres(struct dlm_ctxt *dlm,
 	res->migration_pending = 0;
 	res->inflight_locks = 0;
 
-	/* put in dlm_lockres_release */
-	dlm_grab(dlm);
 	res->dlm = dlm;
 
 	kref_init(&res->refs);
-- 
1.7.1.1