netfilter: ip6_queue: rwlock to spinlock conversion

Converts queue_lock rwlock to a spinlock.

(readlocked part can be changed by reads of integer values)

One atomic operation instead of four per ipq_enqueue_packet() call.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 25 insertions, 32 deletions

diff --git a/net/ipv6/netfilter/ip6_queue.c b/net/ipv6/netfilter/ip6_queue.c
index 8c201743d96d..413ab0754e1f 100644
--- a/net/ipv6/netfilter/ip6_queue.c
+++ b/net/ipv6/netfilter/ip6_queue.c
@@ -43,7 +43,7 @@ typedef int (*ipq_cmpfn)(struct nf_queue_entry *, unsigned long);
 
 static unsigned char copy_mode __read_mostly = IPQ_COPY_NONE;
 static unsigned int queue_maxlen __read_mostly = IPQ_QMAX_DEFAULT;
-static DEFINE_RWLOCK(queue_lock);
+static DEFINE_SPINLOCK(queue_lock);
 static int peer_pid __read_mostly;
 static unsigned int copy_range __read_mostly;
 static unsigned int queue_total;
@@ -73,10 +73,10 @@ __ipq_set_mode(unsigned char mode, unsigned int range)
                 break;
 
         case IPQ_COPY_PACKET:
-                copy_mode = mode;
+                if (range > 0xFFFF)
+                        range = 0xFFFF;
                 copy_range = range;
-                if (copy_range > 0xFFFF)
-                        copy_range = 0xFFFF;
+                copy_mode = mode;
                 break;
 
         default:
@@ -102,7 +102,7 @@ ipq_find_dequeue_entry(unsigned long id)
 {
         struct nf_queue_entry *entry = NULL, *i;
 
-        write_lock_bh(&queue_lock);
+        spin_lock_bh(&queue_lock);
 
         list_for_each_entry(i, &queue_list, list) {
                 if ((unsigned long)i == id) {
@@ -116,7 +116,7 @@ ipq_find_dequeue_entry(unsigned long id)
                 queue_total--;
         }
 
-        write_unlock_bh(&queue_lock);
+        spin_unlock_bh(&queue_lock);
         return entry;
 }
 
@@ -137,9 +137,9 @@ __ipq_flush(ipq_cmpfn cmpfn, unsigned long data)
 static void
 ipq_flush(ipq_cmpfn cmpfn, unsigned long data)
 {
-        write_lock_bh(&queue_lock);
+        spin_lock_bh(&queue_lock);
         __ipq_flush(cmpfn, data);
-        write_unlock_bh(&queue_lock);
+        spin_unlock_bh(&queue_lock);
 }
 
 static struct sk_buff *
@@ -153,9 +153,7 @@ ipq_build_packet_message(struct nf_queue_entry *entry, int *errp)
         struct nlmsghdr *nlh;
         struct timeval tv;
 
-        read_lock_bh(&queue_lock);
-
-        switch (copy_mode) {
+        switch (ACCESS_ONCE(copy_mode)) {
         case IPQ_COPY_META:
         case IPQ_COPY_NONE:
                 size = NLMSG_SPACE(sizeof(*pmsg));
@@ -163,26 +161,21 @@ ipq_build_packet_message(struct nf_queue_entry *entry, int *errp)
 
         case IPQ_COPY_PACKET:
                 if (entry->skb->ip_summed == CHECKSUM_PARTIAL &&
-                    (*errp = skb_checksum_help(entry->skb))) {
-                        read_unlock_bh(&queue_lock);
+                    (*errp = skb_checksum_help(entry->skb)))
                         return NULL;
-                }
-                if (copy_range == 0 || copy_range > entry->skb->len)
+
+                data_len = ACCESS_ONCE(copy_range);
+                if (data_len == 0 || data_len > entry->skb->len)
                         data_len = entry->skb->len;
-                else
-                        data_len = copy_range;
 
                 size = NLMSG_SPACE(sizeof(*pmsg) + data_len);
                 break;
 
         default:
                 *errp = -EINVAL;
-                read_unlock_bh(&queue_lock);
                 return NULL;
         }
 
-        read_unlock_bh(&queue_lock);
-
         skb = alloc_skb(size, GFP_ATOMIC);
         if (!skb)
                 goto nlmsg_failure;
@@ -242,7 +235,7 @@ ipq_enqueue_packet(struct nf_queue_entry *entry, unsigned int queuenum)
         if (nskb == NULL)
                 return status;
 
-        write_lock_bh(&queue_lock);
+        spin_lock_bh(&queue_lock);
 
         if (!peer_pid)
                 goto err_out_free_nskb;
@@ -266,14 +259,14 @@ ipq_enqueue_packet(struct nf_queue_entry *entry, unsigned int queuenum)
 
         __ipq_enqueue_entry(entry);
 
-        write_unlock_bh(&queue_lock);
+        spin_unlock_bh(&queue_lock);
         return status;
 
 err_out_free_nskb:
         kfree_skb(nskb);
 
 err_out_unlock:
-        write_unlock_bh(&queue_lock);
+        spin_unlock_bh(&queue_lock);
         return status;
 }
 
@@ -342,9 +335,9 @@ ipq_set_mode(unsigned char mode, unsigned int range)
 {
         int status;
 
-        write_lock_bh(&queue_lock);
+        spin_lock_bh(&queue_lock);
         status = __ipq_set_mode(mode, range);
-        write_unlock_bh(&queue_lock);
+        spin_unlock_bh(&queue_lock);
         return status;
 }
 
@@ -441,11 +434,11 @@ __ipq_rcv_skb(struct sk_buff *skb)
         if (security_netlink_recv(skb, CAP_NET_ADMIN))
                 RCV_SKB_FAIL(-EPERM);
 
-        write_lock_bh(&queue_lock);
+        spin_lock_bh(&queue_lock);
 
         if (peer_pid) {
                 if (peer_pid != pid) {
-                        write_unlock_bh(&queue_lock);
+                        spin_unlock_bh(&queue_lock);
                         RCV_SKB_FAIL(-EBUSY);
                 }
         } else {
@@ -453,7 +446,7 @@ __ipq_rcv_skb(struct sk_buff *skb)
                 peer_pid = pid;
         }
 
-        write_unlock_bh(&queue_lock);
+        spin_unlock_bh(&queue_lock);
 
         status = ipq_receive_peer(NLMSG_DATA(nlh), type,
                                   nlmsglen - NLMSG_LENGTH(0));
@@ -498,10 +491,10 @@ ipq_rcv_nl_event(struct notifier_block *this,
         struct netlink_notify *n = ptr;
 
         if (event == NETLINK_URELEASE && n->protocol == NETLINK_IP6_FW) {
-                write_lock_bh(&queue_lock);
+                spin_lock_bh(&queue_lock);
                 if ((net_eq(n->net, &init_net)) && (n->pid == peer_pid))
                         __ipq_reset();
-                write_unlock_bh(&queue_lock);
+                spin_unlock_bh(&queue_lock);
         }
         return NOTIFY_DONE;
 }
@@ -528,7 +521,7 @@ static ctl_table ipq_table[] = {
 #ifdef CONFIG_PROC_FS
 static int ip6_queue_show(struct seq_file *m, void *v)
 {
-        read_lock_bh(&queue_lock);
+        spin_lock_bh(&queue_lock);
 
         seq_printf(m,
                       "Peer PID          : %d\n"
@@ -546,7 +539,7 @@ static int ip6_queue_show(struct seq_file *m, void *v)
                       queue_dropped,
                       queue_user_dropped);
 
-        read_unlock_bh(&queue_lock);
+        spin_unlock_bh(&queue_lock);
         return 0;
 }