[PATCH v2 3/3] ocfs2: cluster: fix o2hb_dependent_users leak on pin failure

[Joseph Qi]

In o2hb_region_inc_user(), o2hb_dependent_users is incremented
unconditionally before calling o2hb_region_pin().  If the pin fails,
the counter is never decremented and any partially-pinned regions are
never unpinned, since the caller does not call o2hb_region_dec_user()
on error.

The leaked counter causes subsequent o2hb_region_inc_user() calls to
skip pinning entirely (the > 1 check), leaving heartbeat regions
unprotected.

Fix by rolling back on failure: call o2hb_region_unpin(NULL) to release
any partially-pinned regions and decrement o2hb_dependent_users to
restore the pre-increment state.

Fixes: 58a3158a5d17 ("ocfs2/cluster: Pin/unpin o2hb regions")
Signed-off-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
---
 fs/ocfs2/cluster/heartbeat.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c
index b9395835523e2..c25aa2ff3ebc2 100644
--- a/fs/ocfs2/cluster/heartbeat.c
+++ b/fs/ocfs2/cluster/heartbeat.c
@@ -2499,8 +2499,13 @@ static int o2hb_region_inc_user(const char *region_uuid)
 		goto unlock;
 
 	if (bitmap_weight(o2hb_quorum_region_bitmap,
-			   O2NM_MAX_REGIONS) <= O2HB_PIN_CUT_OFF)
+			  O2NM_MAX_REGIONS) <= O2HB_PIN_CUT_OFF) {
 		ret = o2hb_region_pin(NULL, false);
+		if (ret) {
+			o2hb_region_unpin(NULL);
+			o2hb_dependent_users--;
+		}
+	}
 
 unlock:
 	spin_unlock(&o2hb_live_lock);
-- 
2.39.3