IB/mlx4: Fix MTT leakage in resize CQ

When resizing a CQ, MTTs associated with the old CQE buffer were not
freed.  As a result, if any app used resize CQ repeatedly, all MTTs
were eventually exhausted, which led to all memory registration
operations failing until the driver is reloaded.

Once the RESIZE_CQ command returns successfully from FW, FW no longer
accesses the old CQ buffer, so it is safe to deallocate the MTT
entries used by the old CQ buffer.

Finally, if the RESIZE_CQ command fails, the MTTs allocated for the
new CQEs buffer also need to be de-allocated.

This fixes <https://bugs.openfabrics.org/show_bug.cgi?id=1416>.
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mlx4/cq.c

@@ -343,6 +343,7 @@ int mlx4_ib_resize_cq(struct ib_cq *ibcq, int entries, struct ib_udata *udata)
 {
 	struct mlx4_ib_dev *dev = to_mdev(ibcq->device);
 	struct mlx4_ib_cq *cq = to_mcq(ibcq);
+	struct mlx4_mtt mtt;
 	int outst_cqe;
 	int err;
 
@@ -376,10 +377,13 @@ int mlx4_ib_resize_cq(struct ib_cq *ibcq, int entries, struct ib_udata *udata)
 			goto out;
 	}
 
+	mtt = cq->buf.mtt;
+
 	err = mlx4_cq_resize(dev->dev, &cq->mcq, entries, &cq->resize_buf->buf.mtt);
 	if (err)
 		goto err_buf;
 
+	mlx4_mtt_cleanup(dev->dev, &mtt);
 	if (ibcq->uobject) {
 		cq->buf      = cq->resize_buf->buf;
 		cq->ibcq.cqe = cq->resize_buf->cqe;
@@ -406,6 +410,7 @@ int mlx4_ib_resize_cq(struct ib_cq *ibcq, int entries, struct ib_udata *udata)
 	goto out;
 
 err_buf:
+	mlx4_mtt_cleanup(dev->dev, &cq->resize_buf->buf.mtt);
 	if (!ibcq->uobject)
 		mlx4_ib_free_cq_buf(dev, &cq->resize_buf->buf,
 				    cq->resize_buf->cqe);