netdev - [PATCH net-next 02/16] net/mlx5e: xsk: Drop the check for XSK state in mlx5e_xsk

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Date:   Fri, 30 Sep 2022 09:28:49 -0700
From:   Saeed Mahameed <saeed@...nel.org>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     Saeed Mahameed <saeedm@...dia.com>, netdev@...r.kernel.org,
        Tariq Toukan <tariqt@...dia.com>,
        Maxim Mikityanskiy <maximmi@...dia.com>
Subject: [PATCH net-next 02/16] net/mlx5e: xsk: Drop the check for XSK state in mlx5e_xsk_wakeup

From: Maxim Mikityanskiy <maximmi@...dia.com>

The MLX5E_CHANNEL_STATE_XSK flag checked in mlx5e_xsk_wakeup indicates
that XSK queues are open, but not necessarily activated. This check is
not very useful, because:

0. Both XSK setup and netdev state transitions take the same state_lock
mutex, so they can't happen at the same time.

1. If the netdev is up, xsk_is_bound can return true only when
MLX5E_CHANNEL_STATE_XSK is set on the corresponding channel.
mlx5e_xsk_wakeup is only called when xsk_is_bound is true.

2. If the XSK socket is bound, and the netdev is going up or down,
mlx5e_xsk_wakeup can take one of two branches, depending on the return
value of napi_if_scheduled_mark_missed:

2.1. True means one of two things: either NAPI was enabled at this
point, which means MLX5E_CHANNEL_STATE_XSK was also set; or NAPI was
disabled, and nothing really happened.

2.2. False means that NAPI was enabled by this point, which also implies
MLX5E_CHANNEL_STATE_XSK was set. Additionally, mlx5e_xsk_wakeup contains
a following check for MLX5E_SQ_STATE_ENABLED on async_icosq, and this
flag implies MLX5E_CHANNEL_STATE_XSK too on XSK channels.

As checking this flag doesn't cut any flows, remove the check.

Signed-off-by: Maxim Mikityanskiy <maximmi@...dia.com>
Reviewed-by: Tariq Toukan <tariqt@...dia.com>
Signed-off-by: Saeed Mahameed <saeedm@...dia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c | 2 +-
 drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c    | 3 ---
 2 files changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
index 5129b9bf534f..d7dfc7d2c058 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
@@ -154,7 +154,7 @@ int mlx5e_open_xsk(struct mlx5e_priv *priv, struct mlx5e_params *params,
 void mlx5e_close_xsk(struct mlx5e_channel *c)
 {
 	clear_bit(MLX5E_CHANNEL_STATE_XSK, c->state);
-	synchronize_net(); /* Sync with the XSK wakeup and with NAPI. */
+	synchronize_net(); /* Sync with NAPI. */

 	mlx5e_close_rq(&c->xskrq);
 	mlx5e_close_cq(&c->xskrq.cq);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c
index 1203d7d5f9bd..c856fc3f197e 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/tx.c
@@ -22,9 +22,6 @@ int mlx5e_xsk_wakeup(struct net_device *dev, u32 qid, u32 flags)

 	c = priv->channels.c[ix];

-	if (unlikely(!test_bit(MLX5E_CHANNEL_STATE_XSK, c->state)))
-		return -EINVAL;
-
 	if (!napi_if_scheduled_mark_missed(&c->napi)) {
 		/* To avoid WQE overrun, don't post a NOP if async_icosq is not
 		 * active and not polled by NAPI. Return 0, because the upcoming
-- 
2.37.3