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

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 <[email protected]>
Reviewed-by: Toke Høiland-Jørgensen <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index a3de752c5178..ed0f89373259 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -1147,7 +1147,9 @@ void page_pool_disable_direct_recycling(struct page_pool *pool)
 	WARN_ON(!test_bit(NAPI_STATE_SCHED, &pool->p.napi->state));
 	WARN_ON(READ_ONCE(pool->p.napi->list_owner) != -1);
 
+	mutex_lock(&page_pools_lock);
 	WRITE_ONCE(pool->p.napi, NULL);
+	mutex_unlock(&page_pools_lock);
 }
 EXPORT_SYMBOL(page_pool_disable_direct_recycling);