IB/qib: Correct reference counting in debugfs qp_stats

This particular reference count is not needed with the rcu protection,
and the current code leaks a reference count, causing a hang in
qib_qp_destroy().

Cc: <stable@vger.kernel.org>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

2 files changed, 2 insertions, 9 deletions

diff --git a/drivers/infiniband/hw/qib/qib_debugfs.c b/drivers/infiniband/hw/qib/qib_debugfs.c
index 799a0c3bffc4..6abd3ed3cd51 100644
--- a/drivers/infiniband/hw/qib/qib_debugfs.c
+++ b/drivers/infiniband/hw/qib/qib_debugfs.c
@@ -193,6 +193,7 @@ static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
         struct qib_qp_iter *iter;
         loff_t n = *pos;
 
+        rcu_read_lock();
         iter = qib_qp_iter_init(s->private);
         if (!iter)
                 return NULL;
@@ -224,7 +225,7 @@ static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 
 static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
 {
-        /* nothing for now */
+        rcu_read_unlock();
 }
 
 static int _qp_stats_seq_show(struct seq_file *s, void *iter_ptr)
diff --git a/drivers/infiniband/hw/qib/qib_qp.c b/drivers/infiniband/hw/qib/qib_qp.c
index 7fcc150d603c..6ddc0264aad2 100644
--- a/drivers/infiniband/hw/qib/qib_qp.c
+++ b/drivers/infiniband/hw/qib/qib_qp.c
@@ -1325,7 +1325,6 @@ int qib_qp_iter_next(struct qib_qp_iter *iter)
         struct qib_qp *pqp = iter->qp;
         struct qib_qp *qp;
 
-        rcu_read_lock();
         for (; n < dev->qp_table_size; n++) {
                 if (pqp)
                         qp = rcu_dereference(pqp->next);
@@ -1333,18 +1332,11 @@ int qib_qp_iter_next(struct qib_qp_iter *iter)
                         qp = rcu_dereference(dev->qp_table[n]);
                 pqp = qp;
                 if (qp) {
-                        if (iter->qp)
-                                atomic_dec(&iter->qp->refcount);
-                        atomic_inc(&qp->refcount);
-                        rcu_read_unlock();
                         iter->qp = qp;
                         iter->n = n;
                         return 0;
                 }
         }
-        rcu_read_unlock();
-        if (iter->qp)
-                atomic_dec(&iter->qp->refcount);
         return ret;
 }