[PATCH mlx5-next 07/10] RDMA/mlx5: Extract IB specific lock out of data direct
From: Tariq Toukan <tariqt@nvidia.com>
Date: 2026-09-17 11:15:54
Also in:
linux-rdma, lkml
Subsystem:
infiniband subsystem, mellanox mlx5 ib driver, the rest · Maintainers:
Jason Gunthorpe, Leon Romanovsky, Linus Torvalds
From: Dragos Tatulea <dtatulea@nvidia.com> The data_direct_lock from struct mlx5_ib_dev is an IB specific lock. It protects from unbind while mlx5_data_direct_dev is being accessed. So move data_direct_lock out of the generic bind/unbind functions and into the IB specific notifier callback. data_direct_dev can be set during bind/unbind with a simple WRITE_ONCE, the lock is no longer needed. Each user of the data direct registration API has to do their own locking if necessary. During unbind, the data_direct_dev is set to NULL before calling the notifiers to avoid multiple users still accessing the data_direct_dev while unbind is in progress. This is to avoid another data direct specific lock which can lead to lock ordering issues. This patch has no functional changes. Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com> Reviewed-by: Cosmin Ratiu <redacted> Reviewed-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: Tariq Toukan <tariqt@nvidia.com> --- drivers/infiniband/hw/mlx5/data_direct.c | 8 ++------ drivers/infiniband/hw/mlx5/main.c | 2 ++ drivers/infiniband/hw/mlx5/mlx5_ib.h | 4 +++- drivers/infiniband/hw/mlx5/mr.c | 2 +- drivers/infiniband/hw/mlx5/std_types.c | 2 +- 5 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/drivers/infiniband/hw/mlx5/data_direct.c b/drivers/infiniband/hw/mlx5/data_direct.c
index f871e3ce9f73..16afacdd3601 100644
--- a/drivers/infiniband/hw/mlx5/data_direct.c
+++ b/drivers/infiniband/hw/mlx5/data_direct.c@@ -197,9 +197,7 @@ mlx5_data_direct_get_reg(struct mlx5_ib_dev *ibdev) static void mlx5_data_direct_bind(struct mlx5_ib_dev *ibdev, struct mlx5_data_direct_dev *dev) { - mutex_lock(&ibdev->data_direct_lock); - ibdev->data_direct_dev = dev; - mutex_unlock(&ibdev->data_direct_lock); + WRITE_ONCE(ibdev->data_direct_dev, dev); } static void
@@ -207,11 +205,9 @@ mlx5_data_direct_do_unbind(struct mlx5_data_direct_registration *reg) { struct mlx5_ib_dev *ibdev = reg->ibdev; - mutex_lock(&ibdev->data_direct_lock); + WRITE_ONCE(ibdev->data_direct_dev, NULL); blocking_notifier_call_chain(®->users, MLX5_DATA_DIRECT_UNBIND, NULL); - ibdev->data_direct_dev = NULL; - mutex_unlock(&ibdev->data_direct_lock); } int mlx5_data_direct_init(struct mlx5_ib_dev *ibdev)
diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
index d0141509870a..cefbcc816651 100644
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c@@ -3948,7 +3948,9 @@ static int mlx5_ib_data_direct_event(struct notifier_block *nb, if (action != MLX5_DATA_DIRECT_UNBIND) return NOTIFY_DONE; + mutex_lock(&dev->data_direct_lock); mlx5_ib_revoke_data_direct_mrs(dev); + mutex_unlock(&dev->data_direct_lock); return NOTIFY_OK; }
diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
index e56f3eee7ba1..8792e10340c5 100644
--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h@@ -1092,7 +1092,9 @@ struct mlx5_ib_dev { struct ib_device ib_dev; struct mlx5_core_dev *mdev; struct mlx5_data_direct_dev *data_direct_dev; - /* protect accessing data_direct_dev */ + /* Protects data_direct_mr_list and serializes mr + * registration/deregistration with data direct device unbind. + */ struct mutex data_direct_lock; struct notifier_block mdev_events; struct notifier_block sys_error_events;
diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index e6b74955d95d..1fc61a680f8a 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c@@ -997,7 +997,7 @@ reg_user_mr_dmabuf_by_data_direct(struct ib_pd *pd, u64 offset, return ERR_PTR(-EOPNOTSUPP); mutex_lock(&dev->data_direct_lock); - data_direct_dev = dev->data_direct_dev; + data_direct_dev = READ_ONCE(dev->data_direct_dev); if (!data_direct_dev) { ret = -EINVAL; goto end;
diff --git a/drivers/infiniband/hw/mlx5/std_types.c b/drivers/infiniband/hw/mlx5/std_types.c
index 1ee31611b4b3..df949fa634c9 100644
--- a/drivers/infiniband/hw/mlx5/std_types.c
+++ b/drivers/infiniband/hw/mlx5/std_types.c@@ -203,7 +203,7 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_GET_DATA_DIRECT_SYSFS_PATH)( return PTR_ERR(c); dev = to_mdev(c->ibucontext.device); mutex_lock(&dev->data_direct_lock); - data_direct_dev = dev->data_direct_dev; + data_direct_dev = READ_ONCE(dev->data_direct_dev); if (!data_direct_dev) { ret = -ENODEV; goto end;
--
2.44.0