ocfs2/dlm: remove BUG_ON in a rare case

For migration, we are waiting for DLM_LOCK_RES_MIGRATING flag to be set before sending DLM_MIG_LOCKRES_MSG message to the target. We are using dlm_migration_can_proceed() for that purpose. while, dlm_migration_can_proceed() also returns "go ahead" if target node is down. In this rare case, the DLM_LOCK_RES_MIGRATING maybe is not set yet. Remove the BUG_ON() in this case.

Signed-off-by Wengang Wang<[email protected]>

---
  fs/ocfs2/dlm/dlmmaster.c |   22 ++++++++++++++--------
  1 files changed, 14 insertions(+), 8 deletions(-)

fs/ocfs2/dlm/dlmmaster.c +14 -8

index 4a7506a..94b97fc 100644
@@ -2808,14 +2808,8 @@ again:
  		mlog(0, "trying again...\n");
  		goto again;
  	}
-	/* now that we are sure the MIGRATING state is there, drop
-	 * the unneded state which blocked threads trying to DIRTY */
-	spin_lock(&res->spinlock);
-	BUG_ON(!(res->state&  DLM_LOCK_RES_BLOCK_DIRTY));
-	BUG_ON(!(res->state&  DLM_LOCK_RES_MIGRATING));
-	res->state&= ~DLM_LOCK_RES_BLOCK_DIRTY;
-	spin_unlock(&res->spinlock);
 
+	ret = 0;
  	/* did the target go down or die? */
  	spin_lock(&dlm->spinlock);
  	if (!test_bit(target, dlm->domain_map)) {

@@ -2826,9 +2820,21 @@ again:
  	spin_unlock(&dlm->spinlock);
 
  	/*
+	 * if target is down, we need to clear DLM_LOCK_RES_BLOCK_DIRTY for
+	 * another try; otherwise, we are sure the MIGRATING state is there,
+	 * drop the unneded state which blocked threads trying to DIRTY
+	 */
+	spin_lock(&res->spinlock);
+	BUG_ON(!(res->state&  DLM_LOCK_RES_BLOCK_DIRTY));
+	res->state&= ~DLM_LOCK_RES_BLOCK_DIRTY;
+	if (!ret)
+		BUG_ON(!(res->state&  DLM_LOCK_RES_MIGRATING));
+	spin_unlock(&res->spinlock);
+
+	/*
  	 * at this point:
  	 *
-	 *   o the DLM_LOCK_RES_MIGRATING flag is set
+	 *   o the DLM_LOCK_RES_MIGRATING flag is set if target not down
  	 *   o there are no pending asts on this lockres
  	 *   o all processes trying to reserve an ast on this
  	 *     lockres must wait for the MIGRATING flag to clear

For migration, we are waiting for DLM_LOCK_RES_MIGRATING flag to be set before sending DLM_MIG_LOCKRES_MSG message to the target. We are using dlm_migration_can_proceed() for that purpose. while, dlm_migration_can_proceed() also returns "go ahead" if target node is down. In this rare case, the DLM_LOCK_RES_MIGRATING maybe is not set yet. Remove the BUG_ON() in this case.

Signed-off-by Wengang Wang <[email protected]>