Merge: CNB97: net: page_pool: avoid false positive warning if NAPI was never added

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/6973

JIRA: https://issues.redhat.com/browse/RHEL-93737

Commits:
```
3e61103 ("page_pool: remove WARN_ON() with OR")
c1e00bc ("net: page_pool: avoid false positive warning if NAPI was never added")
```

Signed-off-by: Ivan Vecera <ivecera@redhat.com>

Approved-by: Michal Schmidt <mschmidt@redhat.com>
Approved-by: Davide Caratti <dcaratti@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Augusto Caringi <acaringi@redhat.com>

Author: caringi

net/core/dev.h

@@ -246,4 +246,16 @@ static inline void netdev_set_gro_flush_timeout(struct net_device *netdev,
 
 int rps_cpumask_housekeeping(struct cpumask *mask);
 
+/* Best effort check that NAPI is not idle (can't be scheduled to run) */
+static inline void napi_assert_will_not_race(const struct napi_struct *napi)
+{
+	/* uninitialized instance, can't race */
+	if (!napi->poll_list.next)
+		return;
+
+	/* SCHED bit is set on disabled instances */
+	WARN_ON(!test_bit(NAPI_STATE_SCHED, &napi->state));
+	WARN_ON(READ_ONCE(napi->list_owner) != -1);
+}
+
 #endif

net/core/page_pool.c

@@ -23,6 +23,7 @@
 
 #include <trace/events/page_pool.h>
 
+#include "dev.h"
 #include "page_pool_priv.h"
 
 #define DEFER_TIME (msecs_to_jiffies(1000))
@@ -1076,11 +1077,7 @@ void page_pool_disable_direct_recycling(struct page_pool *pool)
 	if (!pool->p.napi)
 		return;
 
-	/* To avoid races with recycling and additional barriers make sure
-	 * pool and NAPI are unlinked when NAPI is disabled.
-	 */
-	WARN_ON(!test_bit(NAPI_STATE_SCHED, &pool->p.napi->state) ||
-		READ_ONCE(pool->p.napi->list_owner) != -1);
+	napi_assert_will_not_race(pool->p.napi);
 
 	mutex_lock(&page_pools_lock);
 	WRITE_ONCE(pool->p.napi, NULL);