[Ocfs2-devel] [PATCH] ocfs2/dlm: move lock to the tail of grant queue while doing in-place convert

[xuejiufei <xuejiufei@huawei.com>]

We have found a bug when two nodes doing umount one after another.
1) Node 1 migrate a lockres that has 3 locks in grant queue such as
N2(PR)<->N3(NL)<->N4(PR) to N2. After migration, lvb of the lock N3(NL)
and N4(PR) are empty on node 2 because migration target do not copy lvb
to these two lock.
2) Node 3 want to convert to PR, it can be granted in
__dlmconvert_master(), and the order of these locks is unchanged. The
lvb of the lock N3(PR) on node 2 is copyed from lockres in function
dlm_update_lvb() while the lvb of lock N4(PR) is still empty.
3) Node 2 want to leave domain, it will migrate this lockres to node 3.
Then node 2 will trigger the BUG in dlm_prepare_lvb_for_migration()
when adding the lock N4(PR) to mres with the following message because
the lvb of mres is already copied from lock N3(PR), but the lvb of lock
N4(PR) is empty.

"Mismatched lvb in lock cookie=%u:%llu, name=%.*s, node=%u"

Signed-off-by: xuejiufei <xuejiufei@huawei.com>
---
 fs/ocfs2/dlm/dlmconvert.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/ocfs2/dlm/dlmconvert.c b/fs/ocfs2/dlm/dlmconvert.c
index e36d63f..ae0c9d1 100644
--- a/fs/ocfs2/dlm/dlmconvert.c
+++ b/fs/ocfs2/dlm/dlmconvert.c
@@ -212,6 +212,12 @@ grant:
 	if (lock->lksb->flags & DLM_LKSB_PUT_LVB)
 		memcpy(res->lvb, lock->lksb->lvb, DLM_LVB_LEN);

+	/*
+	 * move the lock to tail because it may be the only lock who has
+	 * a invalid lvb.
+	 */
+	list_move_tail(&lock->list, &res->granted);
+
 	status = DLM_NORMAL;
 	*call_ast = 1;
 	goto unlock_exit;
-- 
1.8.4.3