[PATCH v1 net-next 01/16] af_unix: Add struct unix_vertex in struct unix_sock.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

We will replace the garbage collection algorithm for AF_UNIX,
where we will consider each inflight file descriptor of AF_UNIX
sockets as an edge in a directed graph.

Here, we introduce a new struct unix_vertex representing a vertex
in the graph and add it to struct unix_sock.

In the following patch, we will allocate another struct per edge,
which we finally link to the inflight socket's unix_vertex.edges
when sendmsg() succeeds.

The first time an AF_UNIX socket is passed successfully, we will
link its unix_vertex.entry to a global list.

Also, we will count the number of edges as unix_vertex.out_degree.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 include/net/af_unix.h | 8 ++++++++
 net/unix/af_unix.c    | 1 +
 net/unix/garbage.c    | 9 +++++++++
 3 files changed, 18 insertions(+)

diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 627ea8e2d915..664f6bff60ab 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -22,9 +22,16 @@ extern unsigned int unix_tot_inflight;
 
 void unix_inflight(struct user_struct *user, struct file *fp);
 void unix_notinflight(struct user_struct *user, struct file *fp);
+void unix_init_vertex(struct unix_sock *u);
 void unix_gc(void);
 void wait_for_unix_gc(struct scm_fp_list *fpl);
 
+struct unix_vertex {
+	struct list_head edges;
+	struct list_head entry;
+	unsigned long out_degree;
+};
+
 struct sock *unix_peer_get(struct sock *sk);
 
 #define UNIX_HASH_MOD	(256 - 1)
@@ -62,6 +69,7 @@ struct unix_sock {
 	struct path		path;
 	struct mutex		iolock, bindlock;
 	struct sock		*peer;
+	struct unix_vertex	vertex;
 	struct list_head	link;
 	unsigned long		inflight;
 	spinlock_t		lock;
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 4892e9428c9f..ae145b6f77d8 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -996,6 +996,7 @@ static struct sock *unix_create1(struct net *net, struct socket *sock, int kern,
 	u->path.dentry = NULL;
 	u->path.mnt = NULL;
 	spin_lock_init(&u->lock);
+	unix_init_vertex(u);
 	INIT_LIST_HEAD(&u->link);
 	mutex_init(&u->iolock); /* single task reading lock */
 	mutex_init(&u->bindlock); /* single task binding lock */
diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index 9b8473dd79a4..db9ac289ce08 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -101,6 +101,15 @@ struct unix_sock *unix_get_socket(struct file *filp)
 	return NULL;
 }
 
+void unix_init_vertex(struct unix_sock *u)
+{
+	struct unix_vertex *vertex = &u->vertex;
+
+	vertex->out_degree = 0;
+	INIT_LIST_HEAD(&vertex->edges);
+	INIT_LIST_HEAD(&vertex->entry);
+}
+
 DEFINE_SPINLOCK(unix_gc_lock);
 unsigned int unix_tot_inflight;
 static LIST_HEAD(gc_candidates);
-- 
2.30.2