netdev - Re: [PATCH net] sch_htb: Fix inconsistency when leaf qdisc creation fails

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Message-ID: <69a54b65-fe1d-8c1c-792d-0958778c4379@gmail.com>
Date:   Thu, 26 Aug 2021 09:10:56 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Maxim Mikityanskiy <maximmi@...dia.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>
Cc:     Saeed Mahameed <saeedm@...dia.com>,
        Tariq Toukan <tariqt@...dia.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net] sch_htb: Fix inconsistency when leaf qdisc creation
 fails



On 8/26/21 4:54 AM, Maxim Mikityanskiy wrote:
> In HTB offload mode, qdiscs of leaf classes are grafted to netdev
> queues. sch_htb expects the dev_queue field of these qdiscs to point to
> the corresponding queues. However, qdisc creation may fail, and in that
> case noop_qdisc is used instead. Its dev_queue doesn't point to the
> right queue, so sch_htb can lose track of used netdev queues, which will
> cause internal inconsistencies.
> 
> This commit fixes this bug by keeping track of the netdev queue inside
> struct htb_class. All reads of cl->leaf.q->dev_queue are replaced by the
> new field, the two values are synced on writes, and WARNs are added to
> assert equality of the two values.
> 
> The driver API has changed: when TC_HTB_LEAF_DEL needs to move a queue,
> the driver used to pass the old and new queue IDs to sch_htb. Now that
> there is a new field (offload_queue) in struct htb_class that needs to
> be updated on this operation, the driver will pass the old class ID to
> sch_htb instead (it already knows the new class ID).
> 
> Fixes: d03b195b5aa0 ("sch_htb: Hierarchical QoS hardware offload")
> Signed-off-by: Maxim Mikityanskiy <maximmi@...dia.com>
> Reviewed-by: Tariq Toukan <tariqt@...dia.com>
> ---
>  .../net/ethernet/mellanox/mlx5/core/en/qos.c  | 15 ++-
>  .../net/ethernet/mellanox/mlx5/core/en/qos.h  |  4 +-
>  .../net/ethernet/mellanox/mlx5/core/en_main.c |  3 +-
>  include/net/pkt_cls.h                         |  3 +-
>  net/sched/sch_htb.c                           | 97 ++++++++++++-------
>  5 files changed, 72 insertions(+), 50 deletions(-)

Having one patch touching net/sched and one driver looks odd.

I guess it is not possible to split it ?