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 <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>

diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index ed4cd114180ae8a416766bff8998cae250f734f3..7f405672b089d380f18f77f2e4ae3a19c265cf8d 100644 (file)
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h
@@ -237,7 +237,6 @@ struct page_pool {
        struct {
                struct hlist_node list;
                u64 detach_time;
-               u32 napi_id;
                u32 id;
        } user;
 };

diff --git a/net/core/dev.c b/net/core/dev.c
index afa2282f2604353ad65f78c12da9902e9de0931e..07b2bb1ce64ff79894fae8cca044ff9ed0cc3786 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6708,7 +6708,7 @@ void napi_resume_irqs(unsigned int napi_id)
 static void __napi_hash_add_with_id(struct napi_struct *napi,
                                    unsigned int napi_id)
 {
-       napi->napi_id = napi_id;
+       WRITE_ONCE(napi->napi_id, napi_id);
        hlist_add_head_rcu(&napi->napi_hash_node,
                           &napi_hash[napi->napi_id % HASH_SIZE(napi_hash)]);
 }

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index a3de752c5178de6fcc0e5ffefce7f10f7db9aa0a..ed0f89373259ca5612e5a51d77347882186e13f8 100644 (file)
--- 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);
 

diff --git a/net/core/page_pool_priv.h b/net/core/page_pool_priv.h
index 57439787b9c2b21c8ce3ce066f7650db8f7f27c0..2fb06d5f6d559920610e646f61b92769197eb747 100644 (file)
--- a/net/core/page_pool_priv.h
+++ b/net/core/page_pool_priv.h
@@ -7,6 +7,8 @@
 
 #include "netmem_priv.h"
 
+extern struct mutex page_pools_lock;
+
 s32 page_pool_inflight(const struct page_pool *pool, bool strict);
 
 int page_pool_list(struct page_pool *pool);

diff --git a/net/core/page_pool_user.c b/net/core/page_pool_user.c
index 48335766c1bfd61dda6559748ea3c02380518570..6677e0c2e2565073383dea6970c81f52b6bf9de0 100644 (file)
--- a/net/core/page_pool_user.c
+++ b/net/core/page_pool_user.c
@@ -3,6 +3,7 @@
 #include <linux/mutex.h>
 #include <linux/netdevice.h>
 #include <linux/xarray.h>
+#include <net/busy_poll.h>
 #include <net/net_debug.h>
 #include <net/netdev_rx_queue.h>
 #include <net/page_pool/helpers.h>
@@ -14,10 +15,11 @@
 #include "netdev-genl-gen.h"
 
 static DEFINE_XARRAY_FLAGS(page_pools, XA_FLAGS_ALLOC1);
-/* Protects: page_pools, netdevice->page_pools, pool->slow.netdev, pool->user.
+/* Protects: page_pools, netdevice->page_pools, pool->p.napi, pool->slow.netdev,
+ *     pool->user.
  * Ordering: inside rtnl_lock
  */
-static DEFINE_MUTEX(page_pools_lock);
+DEFINE_MUTEX(page_pools_lock);
 
 /* Page pools are only reachable from user space (via netlink) if they are
  * linked to a netdev at creation time. Following page pool "visibility"
@@ -216,6 +218,7 @@ page_pool_nl_fill(struct sk_buff *rsp, const struct page_pool *pool,
 {
        struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
        size_t inflight, refsz;
+       unsigned int napi_id;
        void *hdr;
 
        hdr = genlmsg_iput(rsp, info);
@@ -229,8 +232,10 @@ page_pool_nl_fill(struct sk_buff *rsp, const struct page_pool *pool,
            nla_put_u32(rsp, NETDEV_A_PAGE_POOL_IFINDEX,
                        pool->slow.netdev->ifindex))
                goto err_cancel;
-       if (pool->user.napi_id &&
-           nla_put_uint(rsp, NETDEV_A_PAGE_POOL_NAPI_ID, pool->user.napi_id))
+
+       napi_id = pool->p.napi ? READ_ONCE(pool->p.napi->napi_id) : 0;
+       if (napi_id >= MIN_NAPI_ID &&
+           nla_put_uint(rsp, NETDEV_A_PAGE_POOL_NAPI_ID, napi_id))
                goto err_cancel;
 
        inflight = page_pool_inflight(pool, false);
@@ -319,8 +324,6 @@ int page_pool_list(struct page_pool *pool)
        if (pool->slow.netdev) {
                hlist_add_head(&pool->user.list,
                               &pool->slow.netdev->page_pools);
-               pool->user.napi_id = pool->p.napi ? pool->p.napi->napi_id : 0;
-
                netdev_nl_page_pool_event(pool, NETDEV_CMD_PAGE_POOL_ADD_NTF);
        }