IB/mlx5: Maintain a single emergency page

The mlx5 driver needs to be able to issue invalidation to ODP MRs
even if it cannot allocate memory. To this end it preallocates
emergency pages to use when the situation arises.

This flow should be extremely rare enough, that we don't need
to worry about contention and therefore a single emergency page
is good enough.

Signed-off-by: Ilya Lesokhin <ilyal@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

1 files changed, 29 insertions, 13 deletions

diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
index d9474b95d8e5..bd565af30d66 100644
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -92,6 +92,12 @@ static LIST_HEAD(mlx5_ib_dev_list);
  */
 static DEFINE_MUTEX(mlx5_ib_multiport_mutex);
 
+/* We can't use an array for xlt_emergency_page because dma_map_single
+ * doesn't work on kernel modules memory
+ */
+static unsigned long xlt_emergency_page;
+static struct mutex xlt_emergency_page_mutex;
+
 struct mlx5_ib_dev *mlx5_ib_get_ibdev_from_mpi(struct mlx5_ib_multiport_info *mpi)
 {
 	struct mlx5_ib_dev *dev;
@@ -1698,17 +1704,10 @@ static struct ib_ucontext *mlx5_ib_alloc_ucontext(struct ib_device *ibdev,
 	context->ibucontext.invalidate_range = &mlx5_ib_invalidate_range;
 #endif
 
-	context->upd_xlt_page = __get_free_page(GFP_KERNEL);
-	if (!context->upd_xlt_page) {
-		err = -ENOMEM;
-		goto out_uars;
-	}
-	mutex_init(&context->upd_xlt_page_mutex);
-
 	if (MLX5_CAP_GEN(dev->mdev, log_max_transport_domain)) {
 		err = mlx5_ib_alloc_transport_domain(dev, &context->tdn);
 		if (err)
-			goto out_page;
+			goto out_uars;
 	}
 
 	INIT_LIST_HEAD(&context->vma_private_list);
@@ -1785,9 +1784,6 @@ out_td:
 	if (MLX5_CAP_GEN(dev->mdev, log_max_transport_domain))
 		mlx5_ib_dealloc_transport_domain(dev, context->tdn);
 
-out_page:
-	free_page(context->upd_xlt_page);
-
 out_uars:
 	deallocate_uars(dev, context);
 
@@ -1813,7 +1809,6 @@ static int mlx5_ib_dealloc_ucontext(struct ib_ucontext *ibcontext)
 	if (MLX5_CAP_GEN(dev->mdev, log_max_transport_domain))
 		mlx5_ib_dealloc_transport_domain(dev, context->tdn);
 
-	free_page(context->upd_xlt_page);
 	deallocate_uars(dev, context);
 	kfree(bfregi->sys_pages);
 	kfree(bfregi->count);
@@ -5292,13 +5287,32 @@ static struct mlx5_interface mlx5_ib_interface = {
 	.protocol	= MLX5_INTERFACE_PROTOCOL_IB,
 };
 
+unsigned long mlx5_ib_get_xlt_emergency_page(void)
+{
+	mutex_lock(&xlt_emergency_page_mutex);
+	return xlt_emergency_page;
+}
+
+void mlx5_ib_put_xlt_emergency_page(void)
+{
+	mutex_unlock(&xlt_emergency_page_mutex);
+}
+
 static int __init mlx5_ib_init(void)
 {
 	int err;
 
+	xlt_emergency_page = __get_free_page(GFP_KERNEL);
+	if (!xlt_emergency_page)
+		return -ENOMEM;
+
+	mutex_init(&xlt_emergency_page_mutex);
+
 	mlx5_ib_event_wq = alloc_ordered_workqueue("mlx5_ib_event_wq", 0);
-	if (!mlx5_ib_event_wq)
+	if (!mlx5_ib_event_wq) {
+		free_page(xlt_emergency_page);
 		return -ENOMEM;
+	}
 
 	mlx5_ib_odp_init();
 
@@ -5311,6 +5325,8 @@ static void __exit mlx5_ib_cleanup(void)
 {
 	mlx5_unregister_interface(&mlx5_ib_interface);
 	destroy_workqueue(mlx5_ib_event_wq);
+	mutex_destroy(&xlt_emergency_page_mutex);
+	free_page(xlt_emergency_page);
 }
 
 module_init(mlx5_ib_init);