ocfs2: document access rules for blocked_lock_list

ocfs2_super->blocked_lock_list and ocfs2_super->blocked_lock_count have some
usage restrictions which aren't immediately obvious to anyone reading the
code. It's a good idea to document this so that we avoid making costly
mistakes in the future.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index 22e334d125d0..d08480580470 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -262,6 +262,12 @@ struct ocfs2_super
         unsigned long dc_wake_sequence;
         unsigned long dc_work_sequence;
 
+        /*
+         * Any thread can add locks to the list, but the downconvert
+         * thread is the only one allowed to remove locks. Any change
+         * to this rule requires updating
+         * ocfs2_downconvert_thread_do_work().
+         */
         struct list_head blocked_lock_list;
         unsigned long blocked_lock_count;