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, 3 insertions, 0 deletions

diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h
index d5a86fb81a49..bb53714813ab 100644
--- a/fs/ocfs2/dlm/dlmcommon.h
+++ b/fs/ocfs2/dlm/dlmcommon.h
@@ -140,6 +140,7 @@ struct dlm_ctxt
         unsigned int purge_count;
         spinlock_t spinlock;
         spinlock_t ast_lock;
+        spinlock_t track_lock;
         char *name;
         u8 node_num;
         u32 key;
@@ -316,6 +317,8 @@ struct dlm_lock_resource
          * put on a list for the dlm thread to run. */
         unsigned long    last_used;
 
+        struct dlm_ctxt *dlm;
+
         unsigned migration_pending:1;
         atomic_t asts_reserved;
         spinlock_t spinlock;