ocfs2/dlm: Fix race in adding/removing lockres' to/from the tracking list

This patch adds a new lock, dlm->tracking_lock, to protect adding/removing
lockres' to/from the dlm->tracking_list. We were previously using dlm->spinlock
for the same, but that proved inadequate as we could be freeing a lockres from
a context that did not hold that lock. As the new lock only protects this list,
we can explicitly take it when removing the lockres from the tracking list.

This bug was exposed when testing multiple processes concurrently flock() the
same file.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/ocfs2/dlm/dlmdomain.c b/fs/ocfs2/dlm/dlmdomain.c
index 63f8125824e8..d8d578f45613 100644
--- a/fs/ocfs2/dlm/dlmdomain.c
+++ b/fs/ocfs2/dlm/dlmdomain.c
@@ -1550,6 +1550,7 @@ static struct dlm_ctxt *dlm_alloc_ctxt(const char *domain,
         spin_lock_init(&dlm->spinlock);
         spin_lock_init(&dlm->master_lock);
         spin_lock_init(&dlm->ast_lock);
+        spin_lock_init(&dlm->track_lock);
         INIT_LIST_HEAD(&dlm->list);
         INIT_LIST_HEAD(&dlm->dirty_list);
         INIT_LIST_HEAD(&dlm->reco.resources);