ocfs2: Add ->set_lvb callback in dlmglue

This allows a lock type to set the value block before downconvert.

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

1 files changed, 29 insertions, 2 deletions

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 9e8ed607173b..faa6f57db703 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -131,6 +131,17 @@ struct ocfs2_lock_res_ops {
         int (*check_downconvert)(struct ocfs2_lock_res *, int);
 
         /*
+         * Allows a lock type to populate the lock value block. This
+         * is called on downconvert, and when we drop a lock.
+         *
+         * Locks that want to use this should set LOCK_TYPE_USES_LVB
+         * in the flags field.
+         *
+         * Called with the lockres spinlock held.
+         */
+        void (*set_lvb)(struct ocfs2_lock_res *);
+
+        /*
          * LOCK_TYPE_* flags which describe the specific requirements
          * of a lock type. Descriptions of each individual flag follow.
          */
@@ -148,7 +159,8 @@ struct ocfs2_lock_res_ops {
 #define LOCK_TYPE_REQUIRES_REFRESH 0x1
 
 /*
- * Indicate that a lock type makes use of the lock value block.
+ * Indicate that a lock type makes use of the lock value block. The
+ * ->set_lvb lock type callback must be defined.
  */
 #define LOCK_TYPE_USES_LVB              0x2
 
@@ -2629,6 +2641,7 @@ static int ocfs2_generic_unblock_lock(struct ocfs2_super *osb,
         int blocking;
         int new_level;
         int ret = 0;
+        int set_lvb = 0;
 
         mlog_entry_void();
 
@@ -2703,9 +2716,23 @@ recheck:
 downconvert:
         ctl->requeue = 0;
 
+        if (lockres->l_ops->flags & LOCK_TYPE_USES_LVB) {
+                if (lockres->l_level == LKM_EXMODE)
+                        set_lvb = 1;
+
+                /*
+                 * We only set the lvb if the lock has been fully
+                 * refreshed - otherwise we risk setting stale
+                 * data. Otherwise, there's no need to actually clear
+                 * out the lvb here as it's value is still valid.
+                 */
+                if (set_lvb && !(lockres->l_flags & OCFS2_LOCK_NEEDS_REFRESH))
+                        lockres->l_ops->set_lvb(lockres);
+        }
+
         ocfs2_prepare_downconvert(lockres, new_level);
         spin_unlock_irqrestore(&lockres->l_lock, flags);
-        ret = ocfs2_downconvert_lock(osb, lockres, new_level, 0);
+        ret = ocfs2_downconvert_lock(osb, lockres, new_level, set_lvb);
 leave:
         mlog_exit(ret);
         return ret;