[PATCH net-next 0/4] net/sched: sch_cake: fixes for accounting and reconfiguration

[Jamal Hadi Salim <jhs@mojatatu.com>]

Four independent fixes in the CAKE qdisc.  Three are follow-ups to the
autorate reconfiguration work around commit 7cbfb180945c ("net/sched:
sch_cake: fix autorate reconfiguration throttling") and the 32-bit
admission-counter wraps fixed in gred/bfifo/plug by commit 4c660ee8c809
("net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue");
the fourth is a dead-code cleanup found while auditing the dump path.

Patch 1 serializes a 'tc qdisc change' with the datapath's autorate
update under the qdisc lock, so the netlink writer and the autorate
writer can no longer lose the configured rate; rate_bps becomes
atomic64_t so the 64-bit store is atomic on 32-bit machines too.

Patch 2 propagates the backlog reduction of the reconfigure-time tin
purge to classful parents, so a CAKE leaf under HTB no longer leaves the
purged packets in the parent's qlen/backlog forever.

Patch 3 widens buffer_used and buffer_max_used to u64.  The u32
accumulator wraps once the resident truesize passes 2^32, bypassing the
over-limit drop loop while the configured limit is a u32 attribute.

Patch 4 drops an unreachable 'nla_nest_end() < 0' error check: the
helper never returns a negative value.

All four are hardening for net-next (no Fixes:, no Cc: stable): the
counter wrap, the missing parent-backlog propagation and the
reconfiguration race all predate any contract we could anchor a
regression on.  Patches 1-2 were reported by Sashiko (gemini) and patch
3 comes from the gred 32-bit-wrap family; patch 4 is a static cleanup.

Jamal Hadi Salim (4):
  net/sched: sch_cake: serialize reconfiguration with the datapath
  net/sched: sch_cake: reduce parent backlog when clearing a tin
  net/sched: sch_cake: widen buffer_used to u64
  net/sched: sch_cake: drop dead nla_nest_end() error check

 net/sched/sch_cake.c | 60 +++++++++++++++++++++++++++++++++-------------------
 1 file changed, 38 insertions(+), 22 deletions(-)

-- 
2.43.0