ocfs2/dlm: Remove BUG_ON from migration in the rare case of a down node

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.  However, if the node is
down, dlm_migration_can_proceed() will also return "go ahead".  In this
rare case, the DLM_LOCK_RES_MIGRATING flag might not be set yet. Remove
the BUG_ON() that trips over this condition.

Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

1 files changed, 14 insertions, 8 deletions

diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 4a7506a4e314..94b97fc6a88e 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -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