ocfs2/dlm: do not purge lockres that is queued for assert master

When workqueue is delayed, it may occur that a lockres is purged while it
is still queued for master assert.  it may trigger BUG() as follows.

N1                                         N2
dlm_get_lockres()
->dlm_do_master_requery
                                  is the master of lockres,
                                  so queue assert_master work

                                  dlm_thread() start running
                                  and purge the lockres

                                  dlm_assert_master_worker()
                                  send assert master message
                                  to other nodes
receiving the assert_master
message, set master to N2

dlmlock_remote() send create_lock message to N2, but receive DLM_IVLOCKID,
if it is RECOVERY lockres, it triggers the BUG().

Another BUG() is triggered when N3 become the new master and send
assert_master to N1, N1 will trigger the BUG() because owner doesn't
match.  So we should not purge lockres when it is queued for assert
master.

Signed-off-by: joyce.xue <xuejiufei@huawei.com>
Reviewed-by: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 42 insertions, 1 deletions

diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 4f4b00e173f238..82abf0cc9a12e2 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -581,6 +581,7 @@ static void dlm_init_lockres(struct dlm_ctxt *dlm,
 	atomic_set(&res->asts_reserved, 0);
 	res->migration_pending = 0;
 	res->inflight_locks = 0;
+	res->inflight_assert_workers = 0;
 
 	res->dlm = dlm;
 
@@ -683,6 +684,43 @@ void dlm_lockres_drop_inflight_ref(struct dlm_ctxt *dlm,
 	wake_up(&res->wq);
 }
 
+void __dlm_lockres_grab_inflight_worker(struct dlm_ctxt *dlm,
+		struct dlm_lock_resource *res)
+{
+	assert_spin_locked(&res->spinlock);
+	res->inflight_assert_workers++;
+	mlog(0, "%s:%.*s: inflight assert worker++: now %u\n",
+			dlm->name, res->lockname.len, res->lockname.name,
+			res->inflight_assert_workers);
+}
+
+static void dlm_lockres_grab_inflight_worker(struct dlm_ctxt *dlm,
+		struct dlm_lock_resource *res)
+{
+	spin_lock(&res->spinlock);
+	__dlm_lockres_grab_inflight_worker(dlm, res);
+	spin_unlock(&res->spinlock);
+}
+
+static void __dlm_lockres_drop_inflight_worker(struct dlm_ctxt *dlm,
+		struct dlm_lock_resource *res)
+{
+	assert_spin_locked(&res->spinlock);
+	BUG_ON(res->inflight_assert_workers == 0);
+	res->inflight_assert_workers--;
+	mlog(0, "%s:%.*s: inflight assert worker--: now %u\n",
+			dlm->name, res->lockname.len, res->lockname.name,
+			res->inflight_assert_workers);
+}
+
+static void dlm_lockres_drop_inflight_worker(struct dlm_ctxt *dlm,
+		struct dlm_lock_resource *res)
+{
+	spin_lock(&res->spinlock);
+	__dlm_lockres_drop_inflight_worker(dlm, res);
+	spin_unlock(&res->spinlock);
+}
+
 /*
  * lookup a lock resource by name.
  * may already exist in the hashtable.
@@ -1603,7 +1641,8 @@ send_response:
 			mlog(ML_ERROR, "failed to dispatch assert master work\n");
 			response = DLM_MASTER_RESP_ERROR;
 			dlm_lockres_put(res);
-		}
+		} else
+			dlm_lockres_grab_inflight_worker(dlm, res);
 	} else {
 		if (res)
 			dlm_lockres_put(res);
@@ -2118,6 +2157,8 @@ static void dlm_assert_master_worker(struct dlm_work_item *item, void *data)
 	dlm_lockres_release_ast(dlm, res);
 
 put:
+	dlm_lockres_drop_inflight_worker(dlm, res);
+
 	dlm_lockres_put(res);
 
 	mlog(0, "finished with dlm_assert_master_worker\n");