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>

2 files changed, 44 insertions, 56 deletions

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 6273772aa30c..a17dda1bbee0 100644
--- 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 eaa88d187cdc..acbd774eeb7c 100644
--- 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);