[PATCH net v2] page_pool: store detach_time as ktime_t to avoid false-negatives

[Jakub Kicinski <kuba@kernel.org>]

While testing other changes in vng I noticed that
nl_netdev.page_pool_check flakes. This never happens in real CI.

Turns out vng may boot and get to that test in less than a second.
page_pool_detached() records the detach time in seconds, so if
vng is fast enough detach time is set to 0. Other code treats
0 as "not detached". detach_time is only used to report the state
to the user, so it's not a huge deal in practice but let's fix it.
Store the raw ktime_t (nanoseconds) instead. A nanosecond value
of 0 is practically impossible.

Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Fixes: 69cb4952b6f6 ("net: page_pool: report when page pool was destroyed")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
v2:
 - make it build
v1: https://lore.kernel.org/4e45407b-5c6b-4832-b403-ea62b1e4bcb5@kernel.org

CC: hawk@kernel.org
CC: ilias.apalodimas@linaro.org
---
 include/net/page_pool/types.h | 2 +-
 net/core/page_pool_user.c     | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index 0d453484a585..cdd95477af7a 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h
@@ -247,7 +247,7 @@ struct page_pool {
 	/* User-facing fields, protected by page_pools_lock */
 	struct {
 		struct hlist_node list;
-		u64 detach_time;
+		ktime_t detach_time;
 		u32 id;
 	} user;
 };
diff --git a/net/core/page_pool_user.c b/net/core/page_pool_user.c
index c82a95beceff..ee5060d8eec0 100644
--- a/net/core/page_pool_user.c
+++ b/net/core/page_pool_user.c
@@ -245,7 +245,7 @@ page_pool_nl_fill(struct sk_buff *rsp, const struct page_pool *pool,
 		goto err_cancel;
 	if (pool->user.detach_time &&
 	    nla_put_uint(rsp, NETDEV_A_PAGE_POOL_DETACH_TIME,
-			 pool->user.detach_time))
+			 ktime_divns(pool->user.detach_time, NSEC_PER_SEC)))
 		goto err_cancel;
 
 	if (pool->mp_ops && pool->mp_ops->nl_fill(pool->mp_priv, rsp, NULL))
@@ -337,7 +337,7 @@ int page_pool_list(struct page_pool *pool)
 void page_pool_detached(struct page_pool *pool)
 {
 	mutex_lock(&page_pools_lock);
-	pool->user.detach_time = ktime_get_boottime_seconds();
+	pool->user.detach_time = ktime_get_boottime();
 	netdev_nl_page_pool_event(pool, NETDEV_CMD_PAGE_POOL_CHANGE_NTF);
 	mutex_unlock(&page_pools_lock);
 }
-- 
2.53.0