From fd89099d635e67f22c3eda263bef1f27f9d5dcb5 Mon Sep 17 00:00:00 2001
From: Leon Romanovsky <leonro@mellanox.com>
Date: Mon, 7 Sep 2020 15:09:15 +0300
Subject: [PATCH 1/1] RDMA/mlx5: Issue FW command to destroy SRQ on reentry
Git-commit: fd89099d635e67f22c3eda263bef1f27f9d5dcb5
Patch-mainline: v5.10
References: git-fixes 

The HW release can fail and leave the system in limbo state, where SRQ is
removed from the table, but can't be destroyed later.  In every reentry,
the initial xa_erase_irq() check will fail.

Rewrite the erase logic to keep index, but don't store the entry
itself. By doing it, we can safely reinsert entry back in the case of
destroy failure.

Link: https://lore.kernel.org/r/20200907120921.476363-4-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Nicolas Morey-Chaisemartin <nmoreychaisemartin@suse.com>
---
 drivers/infiniband/hw/mlx5/srq_cmd.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/srq_cmd.c b/drivers/infiniband/hw/mlx5/srq_cmd.c
index 37aaacebd3f2..c53acbc63d0b 100644
--- a/drivers/infiniband/hw/mlx5/srq_cmd.c
+++ b/drivers/infiniband/hw/mlx5/srq_cmd.c
@@ -596,13 +596,22 @@ void mlx5_cmd_destroy_srq(struct mlx5_ib_dev *dev, struct mlx5_core_srq *srq)
 	struct mlx5_core_srq *tmp;
 	int err;
 
-	tmp = xa_erase_irq(&table->array, srq->srqn);
-	if (!tmp || tmp != srq)
+	/* Delete entry, but leave index occupied */
+	tmp = xa_cmpxchg_irq(&table->array, srq->srqn, srq, XA_ZERO_ENTRY, 0);
+	if (WARN_ON(tmp != srq))
 		return;
 
 	err = destroy_srq_split(dev, srq);
-	if (err)
+	if (err) {
+		/*
+		 * We don't need to check returned result for an error,
+		 * because  we are storing in pre-allocated space xarray
+		 * entry and it can't fail at this stage.
+		 */
+		xa_cmpxchg_irq(&table->array, srq->srqn, XA_ZERO_ENTRY, srq, 0);
 		return;
+	}
+	xa_erase_irq(&table->array, srq->srqn);
 
 	mlx5_core_res_put(&srq->common);
 	wait_for_completion(&srq->common.free);
-- 
2.31.1.5.g533053588dc3