ocfs2: Provide the ocfs2_dlm_lvb_valid() stack API.

The Lock Value Block (LVB) of a DLM lock can be lost when nodes die and
the DLM cannot reconstruct its state.  Clients of the DLM need to know
this.

ocfs2's internal DLM, o2dlm, explicitly zeroes out the LVB when it loses
track of the state.  This is not a standard behavior, but ocfs2 has
always relied on it.  Thus, an o2dlm LVB is always "valid".

ocfs2 now supports both o2dlm and fs/dlm via the stack glue.  When
fs/dlm loses track of an LVBs state, it sets a flag
(DLM_SBF_VALNOTVALID) on the Lock Status Block (LKSB).  The contents of
the LVB may be garbage or merely stale.

ocfs2 doesn't want to try to guess at the validity of the stale LVB.
Instead, it should be checking the VALNOTVALID flag.  As this is the
'standard' way of treating LVBs, we will promote this behavior.

We add a stack glue API ocfs2_dlm_lvb_valid().  It returns non-zero when
the LVB is valid.  o2dlm will always return valid, while fs/dlm will
check VALNOTVALID.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Acked-by: Mark Fasheh <mfasheh@suse.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/ocfs2/stackglue.h b/fs/ocfs2/stackglue.h
index c571af375ef8..03a44d60eac9 100644
--- a/fs/ocfs2/stackglue.h
+++ b/fs/ocfs2/stackglue.h
@@ -186,6 +186,11 @@ struct ocfs2_stack_operations {
         int (*lock_status)(union ocfs2_dlm_lksb *lksb);
 
         /*
+         * Return non-zero if the LVB is valid.
+         */
+        int (*lvb_valid)(union ocfs2_dlm_lksb *lksb);
+
+        /*
          * Pull the lvb pointer off of the stack-specific lksb.
          */
         void *(*lock_lvb)(union ocfs2_dlm_lksb *lksb);
@@ -252,6 +257,7 @@ int ocfs2_dlm_unlock(struct ocfs2_cluster_connection *conn,
                      struct ocfs2_lock_res *astarg);
 
 int ocfs2_dlm_lock_status(union ocfs2_dlm_lksb *lksb);
+int ocfs2_dlm_lvb_valid(union ocfs2_dlm_lksb *lksb);
 void *ocfs2_dlm_lvb(union ocfs2_dlm_lksb *lksb);
 void ocfs2_dlm_dump_lksb(union ocfs2_dlm_lksb *lksb);