Re: [PATCH net v4 1/1] ipmr: account multicast table and route memory

On Tue, Sep 08, 2026 at 11:58:39AM +0000, Zihan Xi wrote:

A netadmin in a user+net namespace can create many IPv4 and IPv6
multicast routing tables with MRT_TABLE and MRT6_TABLE. Each unseen
id allocates an mr_table via the shared mr_table_alloc(), links it
into the per-net list, and leaves it until netns teardown. Those
objects were not charged to memcg, so the host unreclaimable slab
grows with the table count.

Account mr_table allocations with GFP_KERNEL_ACCOUNT and mark the
IPv4/IPv6 MFC caches SLAB_ACCOUNT. This matches the established
handling of IP addresses, routes and alternate interface names.

Unresolved MFC entries are still allocated from softIRQ with
GFP_ATOMIC and are not charged. They expire after 10 seconds and are
bounded by the socket receive queue; see commit 0079ad8e8dc3
("ipmr: remove hard code cache_resolve_queue_len limit").

Not worth a v5, just noting in case Sashiko nit picks on it:

Unresolved MFC entries can be allocated from process context and in this
case they are charged correctly.

Fixes: f0ad0860d01e ("ipv4: ipmr: support multiple tables")
Fixes: d1db275dd3f6 ("ipv6: ip6mr: support multiple tables")
Cc: stable@vger.kernel.org
Reported-by: Vega <redacted>
Assisted-by: LLM
Signed-off-by: Zihan Xi <redacted>

Reviewed-by: Ido Schimmel <idosch@nvidia.com>