[Ocfs2-devel] [PATCH] ocfs2/dlm: the mig_request could be for recovery

[Wengang Wang]

I hit a bug, it's the BUG_ON() in

1780                  * do not allocate a new lock structure. */
1781                 if (ml->node == dlm->node_num) {
1782                         /* MIGRATION ONLY! */
1783                         BUG_ON(!(mres->flags & DLM_MRES_MIGRATION));
1784    
1785                         spin_lock(&res->spinlock);

in dlm_process_recovery_data().

I think it's possible it's a mig_request for recovery in the following case:

1) Node A and node  B have ref on lockres A mastered by node C. So on node C
the is a lock on behalf of A, lock A, on lockres A.
2) For umount, node C is migrating lockres A to node B. the migration mle,
master being node C, new master being node B, is created and added to mle
hashtable.
3) Node B "down". Node A is the recovery master. On node C, lockres A also become
the object to recovery because it's during migration and the new master is the
"down" node B.
4) Node C send mig_request request(for recovery) to node A for lockres A including
lock A.
5) receiving the mig_request from node C(for recovery), node A BUG()ed because of
lock A.

fix:
removing the BUG_ON() is OK.

Well, I can't reproduce the bug. So didn't test the fix.

Signed-off-by: Wengang Wang <wen.gang.wang at oracle.com>
---
 fs/ocfs2/dlm/dlmrecovery.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
index b4f99de..03f17d5 100644
--- a/fs/ocfs2/dlm/dlmrecovery.c
+++ b/fs/ocfs2/dlm/dlmrecovery.c
@@ -1780,7 +1780,6 @@ static int dlm_process_recovery_data(struct dlm_ctxt *dlm,
 		 * do not allocate a new lock structure. */
 		if (ml->node == dlm->node_num) {
 			/* MIGRATION ONLY! */
-			BUG_ON(!(mres->flags & DLM_MRES_MIGRATION));
 
 			spin_lock(&res->spinlock);
 			for (j = DLM_GRANTED_LIST; j <= DLM_BLOCKED_LIST; j++) {
-- 
1.6.6.1