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, 3 deletions

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 6cdeaa76f27f..83d2ddb27186 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -1989,7 +1989,8 @@ static inline int ocfs2_meta_lvb_is_trustable(struct inode *inode,
 {
         struct ocfs2_meta_lvb *lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
 
-        if (lvb->lvb_version == OCFS2_LVB_VERSION
+        if (ocfs2_dlm_lvb_valid(&lockres->l_lksb)
+            && lvb->lvb_version == OCFS2_LVB_VERSION
             && be32_to_cpu(lvb->lvb_igeneration) == inode->i_generation)
                 return 1;
         return 0;
@@ -2382,7 +2383,8 @@ int ocfs2_orphan_scan_lock(struct ocfs2_super *osb, u32 *seqno, int ex)
                 return status;
 
         lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
-        if (lvb->lvb_version == OCFS2_ORPHAN_LVB_VERSION)
+        if (ocfs2_dlm_lvb_valid(&lockres->l_lksb) &&
+            lvb->lvb_version == OCFS2_ORPHAN_LVB_VERSION)
                 *seqno = be32_to_cpu(lvb->lvb_os_seqno);
         return status;
 }
@@ -3627,7 +3629,8 @@ static int ocfs2_refresh_qinfo(struct ocfs2_mem_dqinfo *oinfo)
         struct ocfs2_global_disk_dqinfo *gdinfo;
         int status = 0;
 
-        if (lvb->lvb_version == OCFS2_QINFO_LVB_VERSION) {
+        if (ocfs2_dlm_lvb_valid(&lockres->l_lksb) &&
+            lvb->lvb_version == OCFS2_QINFO_LVB_VERSION) {
                 info->dqi_bgrace = be32_to_cpu(lvb->lvb_bgrace);
                 info->dqi_igrace = be32_to_cpu(lvb->lvb_igrace);
                 oinfo->dqi_syncms = be32_to_cpu(lvb->lvb_syncms);