net: page_pool: don't try to stash the napi id

net: page_pool: don't try to stash the napi id

[ Upstream commit 67e4bb2ced0f2d8fbd414f932daea94ba63ae4c4 ]

Page ppol tried to cache the NAPI ID in page pool info to avoid
having a dependency on the life cycle of the NAPI instance.
Since commit under Fixes the NAPI ID is not populated until
napi_enable() and there's a good chance that page pool is
created before NAPI gets enabled.

Protect the NAPI pointer with the existing page pool mutex,
the reading path already holds it. napi_id itself we need
to READ_ONCE(), it's protected by netdev_lock() which are
not holding in page pool.

Before this patch napi IDs were missing for mlx5:

 # ./cli.py --spec netlink/specs/netdev.yaml --dump page-pool-get

 [{'id': 144, 'ifindex': 2, 'inflight': 3072, 'inflight-mem': 12582912},
  {'id': 143, 'ifindex': 2, 'inflight': 5568, 'inflight-mem': 22806528},
  {'id': 142, 'ifindex': 2, 'inflight': 5120, 'inflight-mem': 20971520},
  {'id': 141, 'ifindex': 2, 'inflight': 4992, 'inflight-mem': 20447232},
  ...

After:

 [{'id': 144, 'ifindex': 2, 'inflight': 3072, 'inflight-mem': 12582912,
   'napi-id': 565},
  {'id': 143, 'ifindex': 2, 'inflight': 4224, 'inflight-mem': 17301504,
   'napi-id': 525},
  {'id': 142, 'ifindex': 2, 'inflight': 4288, 'inflight-mem': 17563648,
   'napi-id': 524},
  ...

Fixes: 86e25f40aa1e ("net: napi: Add napi_config")
Reviewed-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://patch.msgid.link/20250123231620.1086401-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>