unix: Show number of pending scm files of receive queue in fdinfo

Unix sockets like a block box. You never know what is stored there:
there may be a file descriptor holding a mount or a block device,
or there may be whole universes with namespaces, sockets with receive
queues full of sockets etc.

The patch adds a little debug and accounts number of files (not recursive),
which is in receive queue of a unix socket. Sometimes this is useful
to determine, that socket should be investigated or which task should
be killed to put reference counter on a resourse.

v2: Pass correct argument to lockdep

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 3426d6dacc45..17e10fba2152 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -41,6 +41,10 @@ struct unix_skb_parms {
 	u32			consumed;
 } __randomize_layout;
 
+struct scm_stat {
+	u32 nr_fds;
+};
+
 #define UNIXCB(skb)	(*(struct unix_skb_parms *)&((skb)->cb))
 
 #define unix_state_lock(s)	spin_lock(&unix_sk(s)->lock)
@@ -65,6 +69,7 @@ struct unix_sock {
 #define UNIX_GC_MAYBE_CYCLE	1
 	struct socket_wq	peer_wq;
 	wait_queue_entry_t	peer_wake;
+	struct scm_stat		scm_stat;
 };
 
 static inline struct unix_sock *unix_sk(const struct sock *sk)