Re: [PATCH net 2/2] net/mlx5: HWS, fix modify header pool creation race
flat view
From: Moshe Shemesh <hidden>
Date: 2026-10-11 07:57:31
Also in:
linux-rdma
On 10/8/2026 11:42 PM, Alexandre Cassen wrote:
quoted hunk ↗ jump to hunk
mlx5_cmd_hws_modify_header_alloc() creates a pool at the index after the last one if no pool matches the pattern. TC and CT allocate modify headers concurrently, meaning two callers can take the same index and the second call fails with -EBUSY. Its error path also destroys the pool it just created although another caller may already use it. Keep such a pool since cleanup releases it. Tested for regressions on ConnectX-7 with firmware 28.48.1000. Fixes: b36315ca69cb ("net/mlx5: fs, add HWS modify header API function") Signed-off-by: Alexandre Cassen <redacted> --- .../mellanox/mlx5/core/steering/hws/fs_hws.c | 21 +++++++++---------- .../mellanox/mlx5/core/steering/hws/fs_hws.h | 1 + 2 files changed, 11 insertions(+), 11 deletions(-)diff --git a/drivers/net/ethernet/mellanox/mlx5/core/steering/hws/fs_hws.c b/drivers/net/ethernet/mellanox/mlx5/core/steering/hws/fs_hws.c index 66edb42268cb..b387016bb5aa 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/steering/hws/fs_hws.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/steering/hws/fs_hws.c@@ -63,6 +63,7 @@ static int mlx5_fs_init_hws_actions_pool(struct mlx5_core_dev *dev, xa_init(&hws_pool->el2tol3tnl_pools); xa_init(&hws_pool->el2tol2tnl_pools); xa_init(&hws_pool->mh_pools); + mutex_init(&hws_pool->mh_pools_lock); xa_init(&hws_pool->table_dests); xa_init(&hws_pool->vport_dests); xa_init(&hws_pool->vport_vhca_dests);@@ -111,6 +112,7 @@ static void mlx5_fs_cleanup_hws_actions_pool(struct mlx5_fs_hws_context *fs_ctx) xa_for_each(&hws_pool->mh_pools, i, pool) mlx5_fs_destroy_mh_pool(pool, &hws_pool->mh_pools, i); xa_destroy(&hws_pool->mh_pools); + mutex_destroy(&hws_pool->mh_pools_lock); xa_for_each(&hws_pool->el2tol2tnl_pools, i, pool) mlx5_fs_destroy_pr_pool(pool, &hws_pool->el2tol2tnl_pools, i); xa_destroy(&hws_pool->el2tol2tnl_pools);@@ -1474,6 +1476,7 @@ static int mlx5_cmd_hws_modify_header_alloc(struct mlx5_flow_root_namespace *ns, pattern.sz = MLX5_UN_SZ_BYTES(set_add_copy_action_in_auto) * num_actions; pattern.data = modify_actions; + mutex_lock(&hws_pool->mh_pools_lock);
The lock covers more than it has to. The pattern lookup is a linear
scan over all pools with a word by word compare per pool, and it runs
on every rule insertion that needs a modify header allocation. Those scans run in parallel today. Taking the mutex around the whole lookup serializes them on a single namespace wide lock, while only the create-if-missing step needs serializing.
Please keep the lookup out of the lock and re-check under it only on a
miss, roughly:
pool = mlx5_fs_find_mh_pool(hws_pool, &pattern, &cnt);
if (!pool) {
mutex_lock(&hws_pool->mh_pools_lock);
pool = mlx5_fs_find_mh_pool(hws_pool, &pattern, &cnt);
if (!pool)
pool = mlx5_fs_create_mh_pool(ns->dev, &pattern,
&hws_pool->mh_pools,
cnt);
mutex_unlock(&hws_pool->mh_pools_lock);
if (IS_ERR(pool))
return PTR_ERR(pool);
}
Thanks, Moshe.
quoted hunk ↗ jump to hunk
known_pattern = false; xa_for_each(&hws_pool->mh_pools, i, pool) { if (mlx5_fs_hws_mh_pool_match(pool, &pattern)) {@@ -1483,17 +1486,16 @@ static int mlx5_cmd_hws_modify_header_alloc(struct mlx5_flow_root_namespace *ns, cnt++; } - if (!known_pattern) { + if (!known_pattern) pool = mlx5_fs_create_mh_pool(ns->dev, &pattern, &hws_pool->mh_pools, cnt); - if (IS_ERR(pool)) - return PTR_ERR(pool); - } + mutex_unlock(&hws_pool->mh_pools_lock); + if (IS_ERR(pool)) + return PTR_ERR(pool); + mh_data = mlx5_fs_hws_mh_pool_acquire_mh(pool); - if (IS_ERR(mh_data)) { - err = PTR_ERR(mh_data); - goto destroy_pool; - } + if (IS_ERR(mh_data)) + return PTR_ERR(mh_data); hws_action = mh_data->bulk->hws_action; mh_data->data = kmemdup(pattern.data, pattern.sz, GFP_KERNEL); if (!mh_data->data) {@@ -1509,9 +1511,6 @@ static int mlx5_cmd_hws_modify_header_alloc(struct mlx5_flow_root_namespace *ns, release_mh: mlx5_fs_hws_mh_pool_release_mh(pool, mh_data); -destroy_pool: - if (!known_pattern) - mlx5_fs_destroy_mh_pool(pool, &hws_pool->mh_pools, cnt); return err; }diff --git a/drivers/net/ethernet/mellanox/mlx5/core/steering/hws/fs_hws.h b/drivers/net/ethernet/mellanox/mlx5/core/steering/hws/fs_hws.h index 20cdacd8f12e..ee37e2e6d68a 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/steering/hws/fs_hws.h +++ b/drivers/net/ethernet/mellanox/mlx5/core/steering/hws/fs_hws.h@@ -19,6 +19,7 @@ struct mlx5_fs_hws_actions_pool { struct xarray el2tol3tnl_pools; struct xarray el2tol2tnl_pools; struct xarray mh_pools; + struct mutex mh_pools_lock; /* serializes pool lookup and creation */ struct xarray table_dests; struct xarray vport_vhca_dests; struct xarray vport_dests; --2.43.0