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Subject[PATCH 3.2 56/87] ocfs2/dlm: ignore cleaning the migration mle that is inuse
3.2.77-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: xuejiufei <xuejiufei@huawei.com>

commit bef5502de074b6f6fa647b94b73155d675694420 upstream.

We have found that migration source will trigger a BUG that the refcount
of mle is already zero before put when the target is down during
migration. The situation is as follows:

dlm_migrate_lockres
dlm_add_migration_mle
dlm_mark_lockres_migrating
dlm_get_mle_inuse
<<<<<< Now the refcount of the mle is 2.
dlm_send_one_lockres and wait for the target to become the
new master.
<<<<<< o2hb detect the target down and clean the migration
mle. Now the refcount is 1.

dlm_migrate_lockres woken, and put the mle twice when found the target
goes down which trigger the BUG with the following message:

"ERROR: bad mle: ".

Signed-off-by: Jiufei Xue <xuejiufei@huawei.com>
Reviewed-by: Joseph Qi <joseph.qi@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/ocfs2/dlm/dlmmaster.c | 26 +++++++++++++++-----------
1 file changed, 15 insertions(+), 11 deletions(-)

--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -2459,6 +2459,11 @@ static int dlm_migrate_lockres(struct dl
spin_lock(&dlm->master_lock);
ret = dlm_add_migration_mle(dlm, res, mle, &oldmle, name,
namelen, target, dlm->node_num);
+ /* get an extra reference on the mle.
+ * otherwise the assert_master from the new
+ * master will destroy this.
+ */
+ dlm_get_mle_inuse(mle);
spin_unlock(&dlm->master_lock);
spin_unlock(&dlm->spinlock);

@@ -2494,6 +2499,7 @@ fail:
if (mle_added) {
dlm_mle_detach_hb_events(dlm, mle);
dlm_put_mle(mle);
+ dlm_put_mle_inuse(mle);
} else if (mle) {
kmem_cache_free(dlm_mle_cache, mle);
mle = NULL;
@@ -2511,17 +2517,6 @@ fail:
* ensure that all assert_master work is flushed. */
flush_workqueue(dlm->dlm_worker);

- /* get an extra reference on the mle.
- * otherwise the assert_master from the new
- * master will destroy this.
- * also, make sure that all callers of dlm_get_mle
- * take both dlm->spinlock and dlm->master_lock */
- spin_lock(&dlm->spinlock);
- spin_lock(&dlm->master_lock);
- dlm_get_mle_inuse(mle);
- spin_unlock(&dlm->master_lock);
- spin_unlock(&dlm->spinlock);
-
/* notify new node and send all lock state */
/* call send_one_lockres with migration flag.
* this serves as notice to the target node that a
@@ -3249,6 +3244,15 @@ top:
mle->new_master != dead_node)
continue;

+ if (mle->new_master == dead_node && mle->inuse) {
+ mlog(ML_NOTICE, "%s: target %u died during "
+ "migration from %u, the MLE is "
+ "still keep used, ignore it!\n",
+ dlm->name, dead_node,
+ mle->master);
+ continue;
+ }
+
/* If we have reached this point, this mle needs to be
* removed from the list and freed. */
dlm_clean_migration_mle(dlm, mle);
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