netlink: Eliminate kmalloc in netlink dump operation.

Following patch stores struct netlink_callback in netlink_sock
to avoid allocating and freeing it on every netlink dump msg.
Only one dump operation is allowed for a given socket at a time
therefore we can safely convert cb pointer to cb struct inside
netlink_sock.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 6273772..a17dda1 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -595,7 +595,7 @@ static unsigned int netlink_poll(struct file *file, struct socket *sock,
                 * for dumps is performed here. A dump is allowed to continue
                 * if at least half the ring is unused.
                 */
-               while (nlk->cb != NULL && netlink_dump_space(nlk)) {
+               while (nlk->cb_running && netlink_dump_space(nlk)) {
                        err = netlink_dump(sk);
                        if (err < 0) {
                                sk->sk_err = err;
@@ -802,18 +802,6 @@ static void netlink_ring_set_copied(struct sock *sk, struct sk_buff *skb)
 #define netlink_mmap_sendmsg(sk, msg, dst_portid, dst_group, siocb)    0
 #endif /* CONFIG_NETLINK_MMAP */
 
-static void netlink_destroy_callback(struct netlink_callback *cb)
-{
-       kfree_skb(cb->skb);
-       kfree(cb);
-}
-
-static void netlink_consume_callback(struct netlink_callback *cb)
-{
-       consume_skb(cb->skb);
-       kfree(cb);
-}
-
 static void netlink_skb_destructor(struct sk_buff *skb)
 {
 #ifdef CONFIG_NETLINK_MMAP
@@ -872,12 +860,12 @@ static void netlink_sock_destruct(struct sock *sk)
 {
        struct netlink_sock *nlk = nlk_sk(sk);
 
-       if (nlk->cb) {
-               if (nlk->cb->done)
-                       nlk->cb->done(nlk->cb);
+       if (nlk->cb_running) {
+               if (nlk->cb.done)
+                       nlk->cb.done(&nlk->cb);
 
-               module_put(nlk->cb->module);
-               netlink_destroy_callback(nlk->cb);
+               module_put(nlk->cb.module);
+               kfree_skb(nlk->cb.skb);
        }
 
        skb_queue_purge(&sk->sk_receive_queue);
@@ -2350,7 +2338,8 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
 
        skb_free_datagram(sk, skb);
 
-       if (nlk->cb && atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2) {
+       if (nlk->cb_running &&
+           atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2) {
                ret = netlink_dump(sk);
                if (ret) {
                        sk->sk_err = ret;
@@ -2566,13 +2555,12 @@ static int netlink_dump(struct sock *sk)
        int alloc_size;
 
        mutex_lock(nlk->cb_mutex);
-
-       cb = nlk->cb;
-       if (cb == NULL) {
+       if (!nlk->cb_running) {
                err = -EINVAL;
                goto errout_skb;
        }
 
+       cb = &nlk->cb;
        alloc_size = max_t(int, cb->min_dump_alloc, NLMSG_GOODSIZE);
 
        if (!netlink_rx_is_mmaped(sk) &&
@@ -2610,11 +2598,11 @@ static int netlink_dump(struct sock *sk)
 
        if (cb->done)
                cb->done(cb);
-       nlk->cb = NULL;
-       mutex_unlock(nlk->cb_mutex);
 
+       nlk->cb_running = false;
+       mutex_unlock(nlk->cb_mutex);
        module_put(cb->module);
-       netlink_consume_callback(cb);
+       consume_skb(cb->skb);
        return 0;
 
 errout_skb:
@@ -2632,59 +2620,51 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
        struct netlink_sock *nlk;
        int ret;
 
-       cb = kzalloc(sizeof(*cb), GFP_KERNEL);
-       if (cb == NULL)
-               return -ENOBUFS;
-
        /* Memory mapped dump requests need to be copied to avoid looping
         * on the pending state in netlink_mmap_sendmsg() while the CB hold
         * a reference to the skb.
         */
        if (netlink_skb_is_mmaped(skb)) {
                skb = skb_copy(skb, GFP_KERNEL);
-               if (skb == NULL) {
-                       kfree(cb);
+               if (skb == NULL)
                        return -ENOBUFS;
-               }
        } else
                atomic_inc(&skb->users);
 
-       cb->dump = control->dump;
-       cb->done = control->done;
-       cb->nlh = nlh;
-       cb->data = control->data;
-       cb->module = control->module;
-       cb->min_dump_alloc = control->min_dump_alloc;
-       cb->skb = skb;
-
        sk = netlink_lookup(sock_net(ssk), ssk->sk_protocol, NETLINK_CB(skb).portid);
        if (sk == NULL) {
-               netlink_destroy_callback(cb);
-               return -ECONNREFUSED;
+               ret = -ECONNREFUSED;
+               goto error_free;
        }
-       nlk = nlk_sk(sk);
 
+       nlk = nlk_sk(sk);
        mutex_lock(nlk->cb_mutex);
        /* A dump is in progress... */
-       if (nlk->cb) {
-               mutex_unlock(nlk->cb_mutex);
-               netlink_destroy_callback(cb);
+       if (nlk->cb_running) {
                ret = -EBUSY;
-               goto out;
+               goto error_unlock;
        }
        /* add reference of module which cb->dump belongs to */
-       if (!try_module_get(cb->module)) {
-               mutex_unlock(nlk->cb_mutex);
-               netlink_destroy_callback(cb);
+       if (!try_module_get(control->module)) {
                ret = -EPROTONOSUPPORT;
-               goto out;
+               goto error_unlock;
        }
 
-       nlk->cb = cb;
+       cb = &nlk->cb;
+       memset(cb, 0, sizeof(*cb));
+       cb->dump = control->dump;
+       cb->done = control->done;
+       cb->nlh = nlh;
+       cb->data = control->data;
+       cb->module = control->module;
+       cb->min_dump_alloc = control->min_dump_alloc;
+       cb->skb = skb;
+
+       nlk->cb_running = true;
+
        mutex_unlock(nlk->cb_mutex);
 
        ret = netlink_dump(sk);
-out:
        sock_put(sk);
 
        if (ret)
@@ -2694,6 +2674,13 @@ out:
         * signal not to send ACK even if it was requested.
         */
        return -EINTR;
+
+error_unlock:
+       sock_put(sk);
+       mutex_unlock(nlk->cb_mutex);
+error_free:
+       kfree_skb(skb);
+       return ret;
 }
 EXPORT_SYMBOL(__netlink_dump_start);
 
@@ -2916,14 +2903,14 @@ static int netlink_seq_show(struct seq_file *seq, void *v)
                struct sock *s = v;
                struct netlink_sock *nlk = nlk_sk(s);
 
-               seq_printf(seq, "%pK %-3d %-6u %08x %-8d %-8d %pK %-8d %-8d %-8lu\n",
+               seq_printf(seq, "%pK %-3d %-6u %08x %-8d %-8d %d %-8d %-8d %-8lu\n",
                           s,
                           s->sk_protocol,
                           nlk->portid,
                           nlk->groups ? (u32)nlk->groups[0] : 0,
                           sk_rmem_alloc_get(s),
                           sk_wmem_alloc_get(s),
-                          nlk->cb,
+                          nlk->cb_running,
                           atomic_read(&s->sk_refcnt),
                           atomic_read(&s->sk_drops),
                           sock_i_ino(s)

diff --git a/net/netlink/af_netlink.h b/net/netlink/af_netlink.h
index eaa88d1..acbd774 100644 (file)
--- a/net/netlink/af_netlink.h
+++ b/net/netlink/af_netlink.h
@@ -32,7 +32,8 @@ struct netlink_sock {
        unsigned long           *groups;
        unsigned long           state;
        wait_queue_head_t       wait;
-       struct netlink_callback *cb;
+       bool                    cb_running;
+       struct netlink_callback cb;
        struct mutex            *cb_mutex;
        struct mutex            cb_def_mutex;
        void                    (*netlink_rcv)(struct sk_buff *skb);