[PATCH rdma-next] RDMA/mlx5: Free software WCs left on wc_list at CQ destroy

[Edward Srouji]

Software WCs generated by mlx5_ib_generate_wc() are allocated one at a
time and linked onto cq->wc_list. The only thing that ever frees them is
poll_soft_wc(), i.e. a consumer actually reaping them. If the CQ is
destroyed while entries are still linked, those allocations are leaked.

Drain the list in destroy_cq_kernel(). Nothing can be walking wc_list by
then: the poll context is the only walker, notify_work the only thing
that can re-arm it, and both are stopped before post_destroy_cq() runs.

destroy_cq_kernel() is also the error unwind for mlx5_ib_create_cq(), so
move the INIT_LIST_HEAD() of wc_list up next to the other list
initialisations, ahead of anything that can jump to err_cqb.  The driver
object is zero-allocated, and list_for_each_entry_safe() evaluates the
next linkage before testing the loop condition, so draining a wc_list
that is still all zeroes would oops.

Fixes: 25361e02c448 ("IB/mlx5: Generate completions in software")
Reviewed-by: Maher Sanalla <msanalla@xxxxxxxxxx>
Signed-off-by: Edward Srouji <edwards@xxxxxxxxxx>
---
 drivers/infiniband/hw/mlx5/cq.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/mlx5/cq.c b/drivers/infiniband/hw/mlx5/cq.c
index 55ffd7d4de517e6ce3f04c98b4edcd94b12e43b3..2f7ac350c3d8f179ad1d4d8c1181b93f3151c7ce 100644
--- a/drivers/infiniband/hw/mlx5/cq.c
+++ b/drivers/infiniband/hw/mlx5/cq.c
@@ -933,8 +933,19 @@ static int create_cq_kernel(struct mlx5_ib_dev *dev, struct mlx5_ib_cq *cq,
 	return err;
 }
 
+static void drain_soft_wc(struct mlx5_ib_cq *cq)
+{
+	struct mlx5_ib_wc *soft_wc, *next;
+
+	list_for_each_entry_safe(soft_wc, next, &cq->wc_list, list) {
+		list_del(&soft_wc->list);
+		kfree(soft_wc);
+	}
+}
+
 static void destroy_cq_kernel(struct mlx5_ib_dev *dev, struct mlx5_ib_cq *cq)
 {
+	drain_soft_wc(cq);
 	free_cq_buf(dev, &cq->buf);
 	mlx5_db_free(dev->mdev, &cq->db);
 }
@@ -1067,6 +1078,7 @@ int mlx5_ib_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
 	spin_lock_init(&cq->lock);
 	INIT_LIST_HEAD(&cq->list_send_qp);
 	INIT_LIST_HEAD(&cq->list_recv_qp);
+	INIT_LIST_HEAD(&cq->wc_list);
 
 	cqe_size = cache_line_size() == 128 ? 128 : 64;
 	err = create_cq_kernel(dev, cq, entries, cqe_size, &cqb, &index,
@@ -1102,7 +1114,6 @@ int mlx5_ib_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
 	mlx5_ib_dbg(dev, "cqn 0x%x\n", cq->mcq.cqn);
 	cq->mcq.event = mlx5_ib_cq_event;
 
-	INIT_LIST_HEAD(&cq->wc_list);
 	kvfree(cqb);
 	return 0;
 

---
base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
change-id: 20261103-free-sw-wcs-8cf40aa66fd8

Best regards,
-- 
Edward Srouji <edwards@xxxxxxxxxx>