net: page_pool: mute the periodic warning for visible page pools

Mute the periodic "stalled pool shutdown" warning if the page pool
is visible to user space. Rolling out a driver using page pools
to just a few hundred hosts at Meta surfaces applications which
fail to reap their broken sockets. Obviously it's best if the
applications are fixed, but we don't generally print warnings
for application resource leaks. Admins can now depend on the
netlink interface for getting page pool info to detect buggy
apps.

While at it throw in the ID of the pool into the message,
in rare cases (pools from destroyed netns) this will make
finding the pool with a debugger easier.
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/core/page_pool.c

@@ -897,18 +897,21 @@ static void page_pool_release_retry(struct work_struct *wq)
 {
 	struct delayed_work *dwq = to_delayed_work(wq);
 	struct page_pool *pool = container_of(dwq, typeof(*pool), release_dw);
+	void *netdev;
 	int inflight;
 
 	inflight = page_pool_release(pool);
 	if (!inflight)
 		return;
 
-	/* Periodic warning */
-	if (time_after_eq(jiffies, pool->defer_warn)) {
+	/* Periodic warning for page pools the user can't see */
+	netdev = READ_ONCE(pool->slow.netdev);
+	if (time_after_eq(jiffies, pool->defer_warn) &&
+	    (!netdev || netdev == NET_PTR_POISON)) {
 		int sec = (s32)((u32)jiffies - (u32)pool->defer_start) / HZ;
 
-		pr_warn("%s() stalled pool shutdown %d inflight %d sec\n",
-			__func__, inflight, sec);
+		pr_warn("%s() stalled pool shutdown: id %u, %d inflight %d sec\n",
+			__func__, pool->user.id, inflight, sec);
 		pool->defer_warn = jiffies + DEFER_WARN_INTERVAL;
 	}