[Cluster-devel] [PATCH dlm/next 2/3] fs: dlm: avoid double list_add() for lkb->lkb_cb_list

[Alexander Aring <aahringo@redhat.com>]

The dlm_add_cb() can run multiple times for a lkb to add a callback and
calling list_add() to calling queue_work() for later. If it's getting
called multiple times while test_bit(LSFL_CB_DELAY, &ls->ls_flags)
is true we need to ensure it was added only once or the list getting
corrupted. The list holder lkb->lkb_cb_list is being used with
list_del_init()/INIT_LIST_HEAD() and can be used with list_empty()
to check if it is not being part of a list.

Cc: stable at vger.kernel.org
Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 fs/dlm/ast.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/dlm/ast.c b/fs/dlm/ast.c
index a44cc42b6317..0271796d36b1 100644
--- a/fs/dlm/ast.c
+++ b/fs/dlm/ast.c
@@ -202,7 +202,8 @@ void dlm_add_cb(struct dlm_lkb *lkb, uint32_t flags, int mode, int status,
 
 		mutex_lock(&ls->ls_cb_mutex);
 		if (test_bit(LSFL_CB_DELAY, &ls->ls_flags)) {
-			list_add(&lkb->lkb_cb_list, &ls->ls_cb_delay);
+			if (list_empty(&lkb->lkb_cb_list))
+				list_add(&lkb->lkb_cb_list, &ls->ls_cb_delay);
 		} else {
 			queue_work(ls->ls_callback_wq, &lkb->lkb_cb_work);
 		}
-- 
2.31.1