[Cake] Re: [PATCH net-next 2/4] net/sched/sch_cake: reduce parent backlog when clearing a tin

[netdev-bot+sashiko@kernel.org]

Thank you for your contribution! Sashiko AI review found more severe
issue(s) in other patches of this series. This mail is only an FYI, in case
you want to address the nit picks below when you respin.

Low priority / nit picks for your consideration:

- [Low] The commit is missing a Fixes: tag.

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net/sched/sch_cake: reduce parent backlog when clearing a tin

This commit changes cake_configure_rates() to record CAKE's qlen and
backlog before and after the purge of unused tins during DiffServ
reconfiguration. It then calls qdisc_tree_reduce_backlog() once with the
difference. Before this, cake_clear_tin() dropped those packets without
updating classful parents such as HTB, so their qlen/backlog accounting
was left wrong.

Link: https://sashiko.dev/#/patchset/20260816012109.2865223-1-ooonea@gmail.com
Link: https://lore.kernel.org/netdev/20260816012109.2865223-1-ooonea@gmail.com/

> CAKE has purged unused tins on DiffServ reconfiguration since commit
> 83f8fd69af4f ("sch_cake: Add DiffServ handling") without propagating the
> resulting backlog reduction to classful parents. The issue was noticed
> while reviewing 7cbfb180945c, but predates that change.

[ ... ]

> Reported-by: Sashiko (gemini) <sashiko-bot@kernel.org>
> Link: https://sashiko.dev/#/patchset/20260816012109.2865223-1-ooonea@gmail.com
> Link: https://lore.kernel.org/netdev/20260816012109.2865223-1-ooonea@gmail.com/
> Reviewed-by: Victor Nogueira <victor@mojatatu.com>
> Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>

[Severity: Low]
Should this patch have a Fixes: tag? The commit message names 83f8fd69af4f
as the commit that added the cake_clear_tin() purge in
cake_configure_rates() without a parent backlog reduction. However, the
only trailers are Reported-by, Link, Reviewed-by and Signed-off-by.

Would it make sense to add something like this:

Fixes: 83f8fd69af4f ("sch_cake: Add DiffServ handling")

so that stable tooling can pick up the fix for older kernels?

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Sashiko AI review · https://netdev-ai.bots.linux.dev/sashiko/#/patchset/QDISC-5RTM.v1.20261007130704%40mojatatu.com