netdev - [PATCH v2 net-next 2/6] af_unix: Include the whole hash table size in UNIX_HASH

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Date:   Mon, 20 Jun 2022 11:51:47 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
CC:     Amit Shah <aams@...zon.com>, Kuniyuki Iwashima <kuniyu@...zon.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>,
        <netdev@...r.kernel.org>
Subject: [PATCH v2 net-next 2/6] af_unix: Include the whole hash table size in UNIX_HASH_SIZE.

Currently, the size of AF_UNIX hash table is UNIX_HASH_SIZE * 2,
the first half for bind()ed sockets and the second half for unbound
ones.  UNIX_HASH_SIZE * 2 is used to define the table and iterate
over it.

In some places, we use ARRAY_SIZE(unix_socket_table) instead of
UNIX_HASH_SIZE * 2.  However, we cannot use it anymore because we
will allocate the hash table dynamically.  Then, we would have to
add UNIX_HASH_SIZE * 2 in many places, which would be troublesome.

This patch adapts the UNIX_HASH_SIZE definition to include bound
and unbound sockets and defines a new UNIX_HASH_MOD macro to ease
calculations.

Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 include/net/af_unix.h |  7 ++++---
 net/unix/af_unix.c    | 18 +++++++++---------
 net/unix/diag.c       |  6 ++----
 3 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index a7ef624ed726..acb56e463db1 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -16,12 +16,13 @@ void wait_for_unix_gc(void);
 struct sock *unix_get_socket(struct file *filp);
 struct sock *unix_peer_get(struct sock *sk);
 
-#define UNIX_HASH_SIZE	256
+#define UNIX_HASH_MOD	(256 - 1)
+#define UNIX_HASH_SIZE	(256 * 2)
 #define UNIX_HASH_BITS	8
 
 extern unsigned int unix_tot_inflight;
-extern spinlock_t unix_table_locks[2 * UNIX_HASH_SIZE];
-extern struct hlist_head unix_socket_table[2 * UNIX_HASH_SIZE];
+extern spinlock_t unix_table_locks[UNIX_HASH_SIZE];
+extern struct hlist_head unix_socket_table[UNIX_HASH_SIZE];
 
 struct unix_address {
 	refcount_t	refcnt;
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 990257f02e7c..c0804ae9c96a 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -118,9 +118,9 @@
 
 #include "scm.h"
 
-spinlock_t unix_table_locks[2 * UNIX_HASH_SIZE];
+spinlock_t unix_table_locks[UNIX_HASH_SIZE];
 EXPORT_SYMBOL_GPL(unix_table_locks);
-struct hlist_head unix_socket_table[2 * UNIX_HASH_SIZE];
+struct hlist_head unix_socket_table[UNIX_HASH_SIZE];
 EXPORT_SYMBOL_GPL(unix_socket_table);
 static atomic_long_t unix_nr_socks;
 
@@ -137,12 +137,12 @@ static unsigned int unix_unbound_hash(struct sock *sk)
 	hash ^= hash >> 8;
 	hash ^= sk->sk_type;
 
-	return UNIX_HASH_SIZE + (hash & (UNIX_HASH_SIZE - 1));
+	return UNIX_HASH_MOD + 1 + (hash & UNIX_HASH_MOD);
 }
 
 static unsigned int unix_bsd_hash(struct inode *i)
 {
-	return i->i_ino & (UNIX_HASH_SIZE - 1);
+	return i->i_ino & UNIX_HASH_MOD;
 }
 
 static unsigned int unix_abstract_hash(struct sockaddr_un *sunaddr,
@@ -155,14 +155,14 @@ static unsigned int unix_abstract_hash(struct sockaddr_un *sunaddr,
 	hash ^= hash >> 8;
 	hash ^= type;
 
-	return hash & (UNIX_HASH_SIZE - 1);
+	return hash & UNIX_HASH_MOD;
 }
 
 static void unix_table_double_lock(unsigned int hash1, unsigned int hash2)
 {
 	/* hash1 and hash2 is never the same because
-	 * one is between 0 and UNIX_HASH_SIZE - 1, and
-	 * another is between UNIX_HASH_SIZE and UNIX_HASH_SIZE * 2.
+	 * one is between 0 and UNIX_HASH_MOD, and
+	 * another is between UNIX_HASH_MOD + 1 and UNIX_HASH_SIZE - 1.
 	 */
 	if (hash1 > hash2)
 		swap(hash1, hash2);
@@ -3239,7 +3239,7 @@ static struct sock *unix_get_first(struct seq_file *seq, loff_t *pos)
 	unsigned long bucket = get_bucket(*pos);
 	struct sock *sk;
 
-	while (bucket < ARRAY_SIZE(unix_socket_table)) {
+	while (bucket < UNIX_HASH_SIZE) {
 		spin_lock(&unix_table_locks[bucket]);
 
 		sk = unix_from_bucket(seq, pos);
@@ -3666,7 +3666,7 @@ static int __init af_unix_init(void)
 
 	BUILD_BUG_ON(sizeof(struct unix_skb_parms) > sizeof_field(struct sk_buff, cb));
 
-	for (i = 0; i < 2 * UNIX_HASH_SIZE; i++)
+	for (i = 0; i < UNIX_HASH_SIZE; i++)
 		spin_lock_init(&unix_table_locks[i]);
 
 	rc = proto_register(&unix_dgram_proto, 1);
diff --git a/net/unix/diag.c b/net/unix/diag.c
index 4e3dc8179fa4..c5d1cca72aa5 100644
--- a/net/unix/diag.c
+++ b/net/unix/diag.c
@@ -204,9 +204,7 @@ static int unix_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
 	s_slot = cb->args[0];
 	num = s_num = cb->args[1];
 
-	for (slot = s_slot;
-	     slot < ARRAY_SIZE(unix_socket_table);
-	     s_num = 0, slot++) {
+	for (slot = s_slot; slot < UNIX_HASH_SIZE; s_num = 0, slot++) {
 		struct sock *sk;
 
 		num = 0;
@@ -242,7 +240,7 @@ static struct sock *unix_lookup_by_ino(unsigned int ino)
 	struct sock *sk;
 	int i;
 
-	for (i = 0; i < ARRAY_SIZE(unix_socket_table); i++) {
+	for (i = 0; i < UNIX_HASH_SIZE; i++) {
 		spin_lock(&unix_table_locks[i]);
 		sk_for_each(sk, &unix_socket_table[i])
 			if (ino == sock_i_ino(sk)) {
-- 
2.30.2