[Ocfs2-devel] [PATCH] ocfs2:fix memory leak in dlm_add_migration_mle

[Xue jiufei]

After some parallel mount/umount test on ocfs2, we got this: slab error
in kmem_cache_destroy(): cache `o2dlm_mle': Can't free all objects.

Then we found a memleak situation in dlm_add_migration_mle().
When a mle found, it will be removed from dlm->hlist. If there is no
pointer to it at that moment, the mle will become an “orphan mle”
that no process can find and release.

Signed-off-by: Xuejiufei <xuejiufei at huawei.com>
---
 fs/ocfs2/dlm/dlmmaster.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 005261c..20d2307 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -284,6 +284,7 @@ static void dlm_init_mle(struct dlm_master_list_entry *mle,
 	mle->master = O2NM_MAX_NODES;
 	mle->new_master = O2NM_MAX_NODES;
 	mle->inuse = 0;
+	mle->assert_master = 0;
 
 	BUG_ON(mle->type != DLM_MLE_BLOCK &&
 	       mle->type != DLM_MLE_MASTER &&
@@ -1743,6 +1744,7 @@ int dlm_assert_master_handler(struct o2net_msg *msg, u32 len, void *data,
 	u32 flags;
 	int master_request = 0, have_lockres_ref = 0;
 	int ret = 0;
+	int bit;
 
 	if (!dlm_grab(dlm))
 		return 0;
@@ -1770,7 +1772,11 @@ int dlm_assert_master_handler(struct o2net_msg *msg, u32 len, void *data,
 		     "MLE for it! (%.*s)\n", assert->node_idx,
 		     namelen, name);
 	} else {
-		int bit = find_next_bit (mle->maybe_map, O2NM_MAX_NODES, 0);
+		spin_lock(&mle->spinlock);
+		mle->assert_master = 1;
+		spin_unlock(&mle->spinlock);
+
+		bit = find_next_bit (mle->maybe_map, O2NM_MAX_NODES, 0);
 		if (bit >= O2NM_MAX_NODES) {
 			/* not necessarily an error, though less likely.
 			 * could be master just re-asserting. */
@@ -3081,6 +3087,8 @@ static int dlm_add_migration_mle(struct dlm_ctxt *dlm,
 			/* remove it so that only one mle will be found */
 			__dlm_unlink_mle(dlm, tmp);
 			__dlm_mle_detach_hb_events(dlm, tmp);
+			if (tmp->type == DLM_MLE_BLOCK && tmp->assert_master == 0)
+				__dlm_put_mle(tmp);
 			ret = DLM_MIGRATE_RESPONSE_MASTERY_REF;
 			mlog(0, "%s:%.*s: master=%u, newmaster=%u, "
 			    "telling master to get ref for cleared out mle "
@@ -3173,6 +3181,7 @@ static void dlm_clean_block_mle(struct dlm_ctxt *dlm,
 		wake_up(&mle->wq);
 
 		/* Do not need events any longer, so detach from heartbeat */
+		__dlm_unlink_mle(dlm, mle);
 		__dlm_mle_detach_hb_events(dlm, mle);
 		__dlm_put_mle(mle);
 	}
-- 
1.7.8.6